Robust pattern recognition system and method using socratic agents

ABSTRACT

A computer-implemented pattern recognition method, system and program product, the method comprising in one embodiment: creating electronically a linkage between a plurality of models within a classifier module within a pattern recognition system such that any one of said plurality of models may be selected as an active model in a recognition process; creating electronically a null hypothesis between at least one model of said plurality of linked models and at least a second model among said plurality of linked models; accumulating electronically evidence to accept or reject said null hypothesis until sufficient evidence is accumulated to reject said null hypothesis in favor of one of said plurality of linked models or until a stopping criterion is met; and transmitting at least a portion of the electronically accumulated evidence or a summary thereof to accept or reject said null hypothesis to a pattern classifier module.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority from Provisional Application U.S.Application 60/844,110, filed Sep. 13, 2006, incorporated herein byreference in its entirety. This application claims priority fromProvisional Application U.S. Application 60/853,031, filed Oct. 20,2006, incorporated herein by reference in its entirety.

BACKGROUND

Although much progress has been made in pattern recognition systems,with the huge and rapidly growing amount of information that needs to beprocessed there is a need for further improvement, especially forsystems that can handle a large quantity of data.

Finally, it is desirable in some embodiments to have a recognitionsystem that is so robust that it can find and correct its own errors.

These objectives and others are addressed by the present invention.

SUMMARY OF THE INVENTION

This invention introduces the concept of Socratic knowledge, named afterthe ancient Greek philosopher, Socrates. In his defense speech at histrial Socrates stated that the only thing that he knew was that hedidn't really know anything. Yet the Delphic oracle had said thatSocrates was the wisest of the Greeks. Socratic knowledge is knowledgeabout knowledge. It is especially knowledge about the limitations ofknowledge, which might be called “wisdom in the sense of Socrates.”

If there are no mistakes in the processing and implementation of apattern recognition system, the performance of the system is primarilydetermined by the knowledge contained in the system, however it might berepresented. In a modern, complex recognition system there may be manyseparate bodies of knowledge. In particular, a complex recognitionsystem may have many separate subsystems, each of which contains its ownset of models to perform a particular pattern recognition task. Eachsuch subsystem will be called a classifier module or a knowledge source.Non-Socratic classifier modules or knowledge sources contain knowledgeabout the patterns or classes being recognized. A Socratic agentcontains knowledge about the knowledge contained in other modules. It isimportant to note that a Socratic agent is not a mere passiverepository, but as it name implies, it is an active process ofmonitoring and measuring the performance of a lower-level module and ofacquiring knowledge about the reliability of the knowledge contained inthat module. The term “Socratic agent” is used generically to describethese higher-level modules that monitor lower-level modules. Onespecialized class of Socratic agents performs a process calleddelayed-decision testing, which will be described shortly. In anotherspecialized case, a single higher-level Socratic module monitors andmanages a whole collection of lower-level classifier modules. Such ahigher-level module is a called a “Socratic controller.” A Socraticcontroller also is an active process, not a mere passive body ofknowledge.

Another key aspect of this invention is the concept of delayed-decisiontesting. One of the simplest forms of Socratic agent is a software agentthat is dedicated to monitoring and performing delayed-decision testingof a single low-level decision. A complex system may have a large numberof such simple delayed-decision Socratic agents active at once.

To take a specific example, consider the difficulty of distinguishingwhether a given training sample is from an unknown component of amixture distribution or is mislabeled and not from the distribution atall. Delayed-decision testing changes the question in an important butsubtle way. Rather than trying to determine from the data itself whichunknown distribution it might be from, the invention instead asks themore direct question, “Will training on this training sample with thegiven label improve the future performance of the system?” Although,just by measuring the training sample and comparing it to exsistingmodels, it would not be possible to know the future performance of thesystem, delayed-decision testing, as its name implies, delays thedecision of whether to accept or skip a training sample until enoughevidence has been accumulated about future performance (where “future”means the future in time relative to the time at which the trainingsample is available although it will no longer be the future by the timeat which the decision is made). Preferably the decision is delayed untilenough evidence has been accumulated to meet a specified level ofstatistical significance.

This “future” data is treated as practice data rather than trainingdata. Specifically, it is used to gather knowledge about the knowledgeand performance of the non-Socratic classifier module that is beingtrained rather than training knowledge about the pattern classesthemselves. Thus, the practice data is used to acquire knowledge in aSocratic agent that is associated with the accept/reject decision forthe particular training sample in question. Because there may be manysuch questionable training samples for a particular non-Socraticclassifier module, there may be a large number of associated Socraticagents acting semi-autonomously as agents on behalf of making morerobust the training of the particular non-Socratic classifier module.Because their decisions are based on statistically significant actual(future) performance, the technique is much more tolerant thannon-Socratic training of errors in the labels of either the trainingdata or the practice data. In fact, Socratic agents can even be used tocorrect the errors in labeling the training data. Furthermore, if a fewmild assumptions are satisfied, the labels of both the training data andthe practice data may be derived from automatic labeling.

Delayed-decision testing and Socratic agents may also be used to performone-shot and structural learning. One-shot learning creates a new modelfrom a single instance of the event being modeled. Non-Socratic trainingadjusts parameters in an existing set of models. Structural learningchanges the structure, such as adding or deleting arcs and nodes inknowledge represented as a graphical structure. Because Socratic agentscan make explicit discrete decisions, they can be used for one-shot andstructural learning as well as to make non-Socratic training morerobust.

A Socratic agent may use arbitrary methods to acquire knowledge aboutthe knowledge of associated classifier modules. In particular, aSocratic agent is not limited to studying a single lower-levelclassifier module, but may model many at once. A Socratic agent thatmodels a collection of related pattern classifiers and performs certainassociated control and management functions is called a “Socraticcontroller.”

In particular, because a Socratic controller can model the comparativeperformance and even the interactions among its collection of associatedclassifier modules, it can manage their joint training to be moreeffective than if each component classifier module is trainedindependently. In particular, the Socratic controller can manage thetraining to actively increase the diversity among the componentclassifier modules.

In another aspect of the invention, a Socratic controller can use itsSocratic knowledge to better create a composite result from theindividual results returned from its component classifier modules. Italso can manage the component classifier modules more efficiently,choosing only a sparse subset of the component classifier modules to beactive at any one time.

In other aspects of the invention, Socratic agents can practicenon-determinism avoiding a decision by creating a new module for eachalternative at a decision point, based on Socratic knowledge thatindicates that the new modules will be complementary. Socraticcontrollers may then be used to manage the collection of modules thatare created. A Socratic agent can also be used to test when an existingmodule in a collection of classifier modules should be deleted becauseit no longer contributes to incremental improvement in the performanceof the collection of modules, given the redundancy with the otherclassifier modules in the collection.

In another aspect of the invention, knowledge may be shared amongclassifier modules. Knowledge or even whole modules may be shared amongsystems in a collection of cooperating systems. With shared knowledgethere is always an issue of whether the knowledge will work in a newenvironment and especially whether it will make an incrementalcontribution in the context of all the other knowledge that is availablein the new environment. The candidate shared knowledge will only beadopted if it improves performance at a statistically significant level,as may be tested by a Socratic agent.

In another aspect of the invention, with the creation and sharing of newknowledge a collection of cooperating recognition systems may be managedas a population of systems, continually evolving and improving.

In another aspect of the invention, a system may be designed to correctits own errors. This aspect is an extension of the method by which aSocratic agent can correct the errors in the designated training data.This process may operate on training data that has been labeledautomatically by running the recognition process. Therefore,interchanging the roles, the output of the regular recognition processmay be designated as automatically labeled training data.Delayed-decision training is performed on this designated training datawith feedback of validated or corrected labels. Switching the roles backagain, the validated or corrected labels may then be used as the final,improved recognition output.

This validation by delayed-decision training introduces a substantialdelay into the recognition process. This delay may be reduced and thesystem made more cost effective by another aspect of the invention. Inthis aspect many streams of data are recognized at the same time by adistributed system of computers with specialized classifier moduleslocated on particular computers rather than copied throughout thesystem. With many streams being recognized at once there is much moredata to accumulate evidence for every active Socratic agent. Thus thetime for each Socratic agent to accumulate enough evidence to bestatistically significant is proportionately reduced.

Briefly, in one embodiment, a computer-implemented pattern recognitionmethod is provided, comprising: creating electronically a linkagebetween a plurality of models within a classifier module within apattern recognition system such that any one of said plurality of modelsmay be selected as an active model in a recognition process; creatingelectronically a null hypothesis between at least one model of saidplurality of linked models and at least a second model among saidplurality of linked models; accumulating electronically evidence toaccept or reject said null hypothesis until sufficient evidence isaccumulated to reject said null hypothesis in favor of one of saidplurality of linked models or until a stopping criterion is met; andtransmitting at least a portion of the electronically accumulatedevidence or a summary thereof to accept or reject said null hypothesisto a pattern classifier module.

In another embodiment, the method further comprises: subsequentlyperforming recognition in which, when one null hypothesis is rejected infavor of a particular one of said plurality of linked models, saidparticular model is selected as the active model in said classifiermodule.

In a yet further embodiment, the method comprises: obtaining a set oftraining data for training said classifier module; obtaining aparticular training sample for said classifier module and an associatedlabel for said training sample; creating a first model for saidclassifier module by training said classifier module on said set oftraining data not including said particular training sample; creating asecond model for said classifier module by training said classifiermodule on said set of training data including said particular trainingsample; and creating said linkage of said plurality of models in whichsaid plurality of models includes at least said first model and saidsecond model.

In a yet further embodiment, the method comprises: annotating saidparticular training sample with the information obtained from saidaccumulating of evidence to accept or reject said null hypothesis.

In a yet further embodiment, the method comprises: performing subsequenttraining skipping training samples and training with changed labels onthe training samples in accord with the annotation obtained from saidaccumulation of evidence to accept or reject said null hypothesis.

In a yet further embodiment, the method comprises: obtaining a pluralityof models resulting from different decisions at a decision point; andcreating said linkage among the plurality of models resulting from thedecision point.

In a yet further embodiment, the method comprises: obtaining a pluralityof models differing from each other by having a differing number ofelements in a given model data structure; creating said linkage amongthe plurality of models having the differing number of elements in thegiven data structure; creating electronically a null hypothesis betweenat least one model of said plurality of linked models and at least asecond model among said plurality of linked models; accumulatingelectronically evidence to accept or reject said null hypothesis untilsufficient evidence is accumulated to reject said null hypothesis infavor of one of said plurality of linked models where the rejectioncriterion is based at least in part on a measure of the marginal costfor the differing number elements or until a stopping criterion is met;and transmitting at least a portion of the electronically accumulatedevidence or a summary thereof to accept or reject said null hypothesisto a pattern classifier module.

In a yet further embodiment, the given data structure is a collection oflower-level models and the elements that differ in number are thelower-level models.

In a yet further embodiment, the method comprises creating at least onelower-level model by one-shot learning, and wherein the lower-levelmodels differ in number at least in part due to the models created byone-shot learning.

In a yet further embodiment, the given data structure is a graphicalstructure and the elements that differ in number are arcs and nodes.

In another embodiment, a computer-implemented method of patternrecognition is provided comprising: obtaining classification results ofa plurality electronic lower level classifier modules performing patternclassification on particular input data; using a higher-level classifiermodule which performs pattern classification on a pattern recognitionproblem different from the plurality of lower-level classifier modules,wherein said higher-level classifier module performs at least one of thefollowing operations: controlling training of the plurality oflower-level classifier modules; combining the results of the pluralityof lower-level classifier modules based at in part on combining rulesthat vary based on the particular input data; and selecting an activesubset of the plurality of lower-level classifier modules based at leastin part on a pattern classification task performed by the higher-levelclassifier module.

In a further embodiment, the higher-level classifier module controls thetraining of the plurality of lower-level classifier modules based atleast in part on data that is not available to any one of thelower-level classifier modules.

In a yet further embodiment, the higher-level classifier module combinesthe results of the plurality of lower-level classifier modules based atleast in part on combining rules that vary based on the particular inputdata and that use data not available to any one of the plurality oflower-level modules.

In a yet further embodiment, the higher-level classifier module selectsan active subset of the lower-level modules during pattern recognitionbased at least in part on a pattern classification task that estimatesreliability of the classification results obtained or to be obtained bythe lower-level classifier modules wherein the higher-level classifiermodule estimates the reliability of the classification results of theplurality of lower-level classifier modules at least in part based ondata not available to any one lower-level classifier module.

In a yet further embodiment, for a given training sample thehigher-level classifier module selects an active subset of the pluralityof lower-level classifier module to be trained on the given trainingsample based at least in part on the higher-level module performing apattern classification to estimate which of the plurality of lower-levelclassifiers will most improve a specified performance measure by beingtrained on the given training sample.

In another embodiment, a computer-implemented method of sharingknowledge among a plurality of pattern classifiers is provided,comprising: obtaining a plurality of classifier modules including afirst classifier module; obtaining a communicable model that is either anew model or a model that has been modified by a knowledge acquisitionprocess in the first classifier module; transmitting said communicablemodel to at least a second classifier module in the plurality ofclassifier modules; creating a pair of model sets for said secondclassifier module in which one member of the pair of model sets is anunmodified model set for the second classifier module and one member ofthe pair of model sets is a modified model set that includes thecommunicable model; testing comparative performance of the pair of modelsets in said second classifier module; and making the modified model setactive in the second classifier module if the modified model setperforms better in said second classifier module.

In a yet another embodiment, the method further comprises transmittingto the first classifier module information obtained from said testing ofthe pair of model sets in said second classifier module.

In a yet further embodiment, the method comprises transmitting saidcommunicable model to at least a third classifier module in theplurality of classifier modules, where the communicable model has notyet been transmitted to said third classifier module; creating a pair ofmodel sets for said third classifier module in which one member of thepair of model sets is an unmodified model set for the third classifiermodule and one member of the pair of model sets is a modified model setthat includes the communicable model; testing comparative performance ofthe pair of model sets in said second classifier module; and making themodified model set electronically active in the second classifier moduleif the modified model set performs better in said second classifiermodule.

In a yet further embodiment, the method comprises: creating softwareassociated with a model or set of models to be transmitted from a firstclassifier module to a second classifier module allowing said model orset of models to be utilized in the context of said second classifier;and transmitted to said second classifier module a module comprising themodel or set of models to be transmitted and the associated software.

In a yet further embodiment, the plurality of classifiers aredistributed among a plurality of recognition systems, furthercomprising: creating at least one new recognition system that hasdifferent subsets of classifier modules from among the plurality ofclassifier modules to thereby obtain an expanded set of recognitionsystems; measuring comparative performance of the expanded set ofrecognition systems; and deleting at least one recognition system fromthe set of recognition systems based on the measurement of comparativeperformance.

In another embodiment, a computer-implemented multi-stage patternrecognition method is provided, comprising: obtaining a sample of datato be recognized; obtaining a plurality of labels for the given samplefrom a set of one or more recognition systems; creating a set of linkedmodel sets for at least one of the one or more recognition systems basedon training said at least one recognition system on the sample of datawherein each model in the set of linked models is created by training onthe given sample with a training label comprising a particular one ofthe plurality of labels obtained for the given sample; obtaining a setof practice data; testing comparative performance of the linked modelsets on the practice data; correcting the label on the given data sampleto agree with the label associated with model from the linked set ofmodels that performs best in the comparative performance testing on thepractice data; and returning a corrected the label as corrected as thefinal recognition result of the multi-stage recognition process.

In a yet further embodiment, the method comprises: obtaining a pluralityof streams of data to be recognized; obtaining a plurality of labels forat least one given sample of data from the plurality of streams from therecognition results of at least one recognition system; creating atleast one set of linked models for the at least one recognition systembased on training said at least one recognition system on the at leastone given sample of data wherein each model in the set of linked modelsis created by training on the given sample with a training label thatcomprises a particular one of the plurality of labels obtained for thegiven sample; obtain practice data from the plurality of streams ofdata; performing comparative performance testing of the linked modelsets on the plurality of streams of data to be recognized; accumulatingthe comparative performance measurements across the plurality of datastreams to be recognized; and reporting as the final recognition resultfor the at least one given sample of data the label value correspondingto the model in the linked set of model that performed best in theaccumulated performance measurements.

In another embodiment, a computer-implemented pattern recognition methodis provided, comprising: creating electronically a linkage between aplurality of models within a classifier module within a patternrecognition system such that any one of said plurality of models may beselected as the active model in the recognition process; collectingevidence of a degree of comparative performance of the plurality oflinked models including estimates of a degree to which errors made byeach two of the linked models are diverse; creating a plurality ofclassifier modules by selecting for each created classifier module adifferent model from the plurality of linked models based at least inpart on evidence of the pair-wise diversity of the errors made by thelinked models.

In a further embodiment, the method comprises creating a plurality ofsystems each comprising a plurality of the classifier modules eachcomprising a different subset of the plurality of created classifiermodules; collecting electronically evidence of the comparativeperformance of the plurality of classifier modules; and discarding atleast one of the plurality of created classifier modules based at leastin part on the collected evidence of comparative performance.

In another embodiment, a system for pattern recognition is provided,comprising: one or more processors that include among them the followingcomponents: a component for creating electronically a linkage between aplurality of models within a classifier module within a patternrecognition system such that any one of said plurality of models may beselected as an active model in a recognition process; a component forcreating electronically a null hypothesis between at least one model ofsaid plurality of linked models and at least a second model among saidplurality of linked models; a component for accumulating electronicallyevidence to accept or reject said null hypothesis until sufficientevidence is accumulated to reject said null hypothesis in favor of oneof said plurality of linked models or until a stopping criterion is met;and a component for transmitting at least a portion of theelectronically accumulated evidence or a summary thereof to accept orreject said null hypothesis to a pattern classifier module.

In another embodiment, a program product for computer-implementedpattern recognition is provided, comprising: one or more computer usablemedia having computer readable program code embodied therein or amongthem if more than one computer usable medium, to be executed by acomputer, the computer readable program code comprising: creatingelectronically a linkage between a plurality of models within aclassifier module within a pattern recognition system such that any oneof said plurality of models may be selected as an active model in arecognition process; creating electronically a null hypothesis betweenat least one model of said plurality of linked models and at least asecond model among said plurality of linked models; accumulatingelectronically evidence to accept or reject said null hypothesis untilsufficient evidence is accumulated to reject said null hypothesis infavor of one of said plurality of linked models or until a stoppingcriterion is met; and transmitting at least a portion of theelectronically accumulated evidence or a summary thereof to accept orreject said null hypothesis to a pattern classifier module.

In another embodiment, a system for pattern recognition is providedcomprising: one or more processors that include among them the followingcomponents: a component for obtaining classification results of aplurality electronic lower level classifier modules performing patternclassification on particular input data; a component for using ahigher-level classifier module which performs pattern classification ona pattern recognition problem different from the plurality oflower-level classifier modules, wherein said higher-level classifiermodule performs at least one of the following operations: controllingtraining of the plurality of lower-level classifier modules; combiningthe results of the plurality of lower-level classifier modules based atin part on combining rules that vary based on the particular input data;and selecting an active subset of the plurality of lower-levelclassifier modules based at least in part on a pattern classificationtask performed by the higher-level classifier module.

In another embodiment, a program product for computer-implementedpattern recognition is provided comprising: one or more computer usablemedia having computer readable program code embodied therein or amongthem if more than one computer usable medium, to be executed by acomputer, the computer readable program code comprising: program codefor obtaining classification results of a plurality electronic lowerlevel classifier modules performing pattern classification on particularinput data; program code for using a higher-level classifier modulewhich performs pattern classification on a pattern recognition problemdifferent from the plurality of lower-level classifier modules, whereinsaid higher-level classifier module performs at least one of thefollowing operations: controlling training of the plurality oflower-level classifier modules; combining the results of the pluralityof lower-level classifier modules based at in part on combining rulesthat vary based on the particular input data; and selecting an activesubset of the plurality of lower-level classifier modules based at leastin part on a pattern classification task performed by the higher-levelclassifier module.

In another embodiment, a system for sharing knowledge among a pluralityof pattern classifiers is provided, comprising: one or more processorsthat include among them the following components: a component forobtaining a plurality of classifier modules including a first classifiermodule; a component for obtaining a communicable model that is either anew model or a model that has been modified by a knowledge acquisitionprocess in the first classifier module; a component for transmittingsaid communicable model to at least a second classifier module in theplurality of classifier modules; a component for creating a pair ofmodel sets for said second classifier module in which one member of thepair of model sets is an unmodified model set for the second classifiermodule and one member of the pair of model sets is a modified model setthat includes the communicable model; a component for testingcomparative performance of the pair of model sets in said secondclassifier module; and a component for making the modified model setactive in the second classifier module if the modified model setperforms better in said second classifier module.

In another embodiment, a program product for computer-implementedsharing of knowledge among a plurality of pattern classifiers isprovided, comprising: one or more computer usable media having computerreadable program code embodied therein or among them if more than onecomputer usable medium, to be executed by a computer, the computerreadable program code comprising: program code for obtaining a pluralityof classifier modules including a first classifier module; program codefor obtaining a communicable model that is either a new model or a modelthat has been modified by a knowledge acquisition process in the firstclassifier module; program code for transmitting said communicable modelto at least a second classifier module in the plurality of classifiermodules; program code for creating a pair of model sets for said secondclassifier module in which one member of the pair of model sets is anunmodified model set for the second classifier module and one member ofthe pair of model sets is a modified model set that includes thecommunicable model; program code for testing comparative performance ofthe pair of model sets in said second classifier module; and programcode for making the modified model set active in the second classifiermodule if the modified model set performs better in said secondclassifier module.

In another embodiment, a system for multi-stage pattern recognition isprovided, comprising: one or more processors that include among them thefollowing components: a component for obtaining a sample of data to berecognized; a component for obtaining a plurality of labels for thegiven sample from a set of one or more recognition systems; a componentfor creating a set of linked model sets for at least one of the one ormore recognition systems based on training said at least one recognitionsystem on the sample of data wherein each model in the set of linkedmodels is created by training on the given sample with a training labelcomprising a particular one of the plurality of labels obtained for thegiven sample; a component for obtaining a set of practice data; acomponent for testing comparative performance of the linked model setson the practice data; a component for correcting the label on the givendata sample to agree with the label associated with model from thelinked set of models that performs best in the comparative performancetesting on the practice data; and a component for returning a correctedthe label as corrected as the final recognition result of themulti-stage recognition process.

In another embodiment, a program product for computer-implementedmulti-stage pattern recognition is provided, comprising: one or morecomputer usable media having computer readable program code embodiedtherein or among them if more than one computer usable medium, to beexecuted by a computer, the computer readable program code comprising:program code for obtaining a sample of data to be recognized; programcode for obtaining a plurality of labels for the given sample from a setof one or more recognition systems; program code for creating a set oflinked model sets for at least one of the one or more recognitionsystems based on training said at least one recognition system on thesample of data wherein each model in the set of linked models is createdby training on the given sample with a training label comprising aparticular one of the plurality of labels obtained for the given sample;program code for obtaining a set of practice data; program code fortesting comparative performance of the linked model sets on the practicedata; program code for correcting the label on the given data sample toagree with the label associated with model from the linked set of modelsthat performs best in the comparative performance testing on thepractice data; and program code for returning a corrected the label ascorrected as the final recognition result of the multi-stage recognitionprocess.

In another embodiment, a system for pattern recognition is provided,comprising: one or more processors that include among them the followingcomponents: a component for creating electronically a linkage between aplurality of models within a classifier module within a patternrecognition system such that any one of said plurality of models may beselected as the active model in the recognition process; a component forcollecting evidence of a degree of comparative performance of theplurality of linked models including estimates of a degree to whicherrors made by each two of the linked models are diverse; and acomponent for creating a plurality of classifier modules by selectingfor each created classifier module a different model from the pluralityof linked models based at least in part on evidence of the pair-wisediversity of the errors made by the linked models.

In another embodiment, a program product for computer-implementedpattern recognition is provided, comprising: one or more computer usablemedia having computer readable program code embodied therein or amongthem if more than one computer usable medium, to be executed by acomputer, the computer readable program code comprising: program codefor creating electronically a linkage between a plurality of modelswithin a classifier module within a pattern recognition system such thatany one of said plurality of models may be selected as the active modelin the recognition process; program code for collecting evidence of adegree of comparative performance of the plurality of linked modelsincluding estimates of a degree to which errors made by each two of thelinked models are diverse; and program code for creating a plurality ofclassifier modules by selecting for each created classifier module adifferent model from the plurality of linked models based at least inpart on evidence of the pair-wise diversity of the errors made by thelinked models.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by reference to the following Figuresand diagrams:

FIG. 1 is a block diagram of a higher level Socratic agent acquiringknowledge about and controlling an associated lower-level classifiermodule.

FIG. 2 is a block diagram of a classifier module and a plurality ofassociated Socratic agents.

FIG. 3 is a flowchart of a process of delayed-decision training.

FIG. 4 is a flowchart of delayed-decision one-shot learning andasymmetric delayed-decision testing, which may be applied to structurelearning.

FIG. 5 is a flowchart of a process of feeding back information about thelabels associated with a given training sample.

FIG. 6 is a flowchart of correcting labels in training data.

FIG. 7 is a flowchart of a process of iteratively correcting the labelsin training and practice data.

FIG. 8 is a block diagram of a Socratic controller with relatedclassifier modules and independent classifier modules.

FIG. 9 is a block diagram of a process of a Socratic controlleracquiring knowledge about the performance of one or more lower-levelclassifier modules.

FIG. 10 is a flowchart of an implementation of the operation of aSocratic controller in the recognition process.

FIG. 11 is a flowchart of an implementation of the operation ofpartitioning a pattern space to create multiple specialized classifiermodules.

FIG. 12 is a flowchart of an implementation of a Socratic controller bypartitioning the data space.

FIG. 13 is a flowchart of a decision tree builder.

FIG. 14 is a flowchart of a process for developing questions of amultiple class decision tree.

FIG. 15 is a flowchart of a process for choosing which component totrain in a multiple classifier system.

FIG. 16 is a flowchart of a process for optimizing control parameters ina system.

FIG. 17 is a flowchart of a process for creating modules bynon-determinism.

FIG. 18 is a flowchart of a process for creating modules by measuringcorrelation and divergence among paired models in a Socratic agent.

FIG. 19 is a flowchart of a process for semi-supervised training of asimplified module by a more computation intensive module.

FIG. 20 is a flowchart of a process for sharing knowledge among modules.

FIG. 21 is a flowchart of a process for managing multiple evolvingsystems.

FIG. 22 is a flowchart of a process for module sharing in a distributedsystem.

FIG. 23 is a flowchart of a process of recognition by feedback fromdelayed decision training on automatically labeled data.

FIG. 24 is a flowchart of a process for sharing resources in thesimultaneous recognition of many channels.

FIG. 25, a block diagram illustrating a computer network forimplementing some aspects of some embodiments of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Explanation of Special Terms:

A knowledge source is an object that includes a mechanism for knowledgerepresentation and either a mechanism for knowledge acquisition or acollection of built-in base knowledge or both.

A classifier module is a processing module that receives samples of datafeatures as input and generates classification results as output. Theclassification results may, for example, comprises an indication of theclass best matching the input data or may comprises a score for eachclass indicating how well the data matches the given class. Implicitly,any pattern classifier has a representation of knowledge about the classit identifies. Generally, a classifier module is trainable and hence hasa mechanism for knowledge acquisition. Therefore, any pattern classifieris a kind of knowledge source. It is to be understood that a classifiermodule is not necessarily implemented as a separate software module oras a separate piece of hardware. A single software module may implementa plurality of classifier modules. A single software module may alsoimplement one or more lower-level modules as well as a higher-levelmodule. In particular, a Socratic controller, which comprises ahigher-level classifier module associated with a plurality oflower-level classifier modules may be implemented as either a singlesoftware module or as a plurality of software modules.

In its simplest form a classifier module chooses which of a finitenumber of pattern classes best matches a given data sample that is to berecognized. However, the phrase “classifier module” is intended to beinterpreted very broadly, and the phrase “classification results” isintended to cover other forms of output. For example, in a systemrecognizing text or speech, a processing module that representsknowledge about likelihoods of word sequences is to be considered a kindof classifier module. In a typical embodiment, the output of such amodule would be represented as a probability distribution of possiblecontinuation words, conditional on the context of the history ofpreceding words.

In isolation, the verbs “classify” and “recognize” are essentiallysynonyms, as are the nouns “classifier” and “recognizer.” However, inthis document “classifier” will generally be used in the context of thephrase “classifier module,” while the morpheme “recognize” willgenerally be used in a phrase such as “recognition system.” A“classifier module” is one module within a recognition system. Arecognition system is a complete stand-alone system, possibly includingmodules to do other tasks as well as one or more classifier modules.Although a recognition system may have only one classifier module, itmay be easier to understand the example embodiments if any reference toa “recognition system” is visualized as a complex system that may havemany “classifier modules” as subsystems.

A model in a classifier module is a collection of data structures anddata and parameter values by which a classifier module characterizes oneor more patterns to be classified. There is some variation of usage asto whether a particular collection of knowledge is referred to as a “setof models” (that is, as a plural) or as a “model” (singular). Forexample, in an optical character recognition system, there might be aseparate model representing each character. So the knowledge about theimages of the characters might be considered to be a set of models.However, the recognition system might also represent knowledge aboutword sequences as information to help resolve ambiguities and correcterror in the low level character recognition. Such knowledge about wordsequences is often represented within a single integrated data structureand referred to as a “language model” rather than as a set of models ofdifferent word sequences. For purposes of this document, the word“model” is to be given the broadest interpretation. The term “model” maybe used to refer to a single simple model, such as a model for a singlecharacter, or it may refer to a more complex modeling structure, such asa language model, or it may refer to a composite model that is composedof a number of individual component models, such as the wordpronunciations in a dictionary. In the context of sharing knowledgeamong systems, the phrase “transmitting a model” from one system toanother system may refer to transmitting any of these forms of model andmay also refer to a process that includes encapsulating the model (whichmay be a composite set of models) in a module, including processingsoftware, and transmitting the module as a package.

A communicable model is a model that is communicable from a firstclassifier module to a second classifier module. There are at leastthree cases in which a model is communicable. In the first case there isa corresponding model in the second classifier module such that themodel in the first classifier may be treated as a modified version ofthe corresponding model in the second classifier module. In the secondcase the communicable module is a new model. A new model is communicableif it is a member of a model set in the first classifier module forwhich there is a corresponding model set in the second classifier moduleand the second classifier module is capable of accepting additions tothat corresponding model set. The third case is when a model isencapsulated in a module with processing software that facilitates theusage of the model in a new context in a different system. In this case,as mentioned earlier, the entire module is transmitted.

A communicable module is a classifier module that contains acommunicable model or set of models. The communicable module may includeprocessing software specifically to help make the model or set of modelscommunicable to a new system.

Structural change in a classifier module or knowledge source is theaddition or deletion of an object in a collection related models or ofan element in a data structure. Most training of pattern classifiersmerely adjusts the values of parameters that control the behavior of theclassifier and do not make any structural changes. In a knowledgerepository, such as a dictionary, if changes are made at all, they tendto be structural changes. For example, in a pronunciation dictionary aword may added or deleted or a pronunciation may be added or deleted toa particular word. Even substituting a new pronunciation for an oldpronunciation would generally be regarded as a structural change ratherthan merely adjustment of parameters. Advanced learning algorithms canalso automatically learn new structure for pattern classifiers.

As an illustrative example, consider an acoustic model for a syllable ina speech recognition system. In one embodiment, the acoustic model for asyllable may be represented as a graph. More specifically, it may berepresented as a labeled directed graph. Such a graph consists of a setof nodes and an associated set of arcs. In general each arc in a graphconnects a pair of nodes. In a directed graph, the arc has direction. Itpoints from the first node in its associated pair of nodes to the secondnode. In an acoustic model in a speech recognition system, there arelabels on either the nodes or the arcs of the directed graph. The labelsidentify short units of sound. In one embodiment, each node is labeledwith an identifier for a short, relatively steady-state sound (notchanging much over its short time interval). The nodes in the graph fora particular syllable represent the sounds that might occur in aninstance of the syllable. The arcs represent the transitions between therelatively steady-state sounds. In one embodiment, there is a designatednode representing the beginning of the syllable and a designated noderepresenting the end of the syllable. Any particular instance of thesyllable is represented by a sequence of nodes and arcs that constitutesa path through the graph from the designated beginning node to thedesignated ending node. Such a path will not necessarily pass throughevery node in the graph, representing the fact that in a given instanceof a syllable not necessarily does every possible sound occur. Morecomplicated graphs may be used to represent additional properties of theacoustic model, such as associated probability distributions and theinfluence of the context on how a syllable is likely to be pronounced.

In this illustrative example, learning structural change in the acousticmodel for a particular syllable would be represented by the addition ordeletion of nodes or arcs to the graph or by changing labels in thegraph. Learning the probability distributions associated with the graphwould be regarded as training parameter values, and not as structurallearning.

A Socratic agent is a higher-level classifier module that containsknowledge about the knowledge of at least one other classifier module.Furthermore, as a classifier module and not a mere knowledge repository,it has active mechanisms for acquiring, evaluating and utilizing thisknowledge about knowledge. It is to be understood that as Socratic agentrepresents knowledge about knowledge, the term “classifier module” is tobe interpreted in the broadest possible sense. For example, oneembodiment of a Socratic agent creates a null hypothesis relative to thecomparative performance of one or more models in the at least one otherclassifier module. Collecting evidence to accept or reject the nullhypothesis is to be understood as a classification task even though itdoes not directly classify the patterns classified by the otherclassifier module, but rather makes a performance-based classificationof versions of the models in the other at least one classifier module. ASocratic agent is named after the ancient Greek philosopher Socrates,who said in his defense speech at his trial, “The only thing that I knowis that I don't really know anything.” Generally, a Socratic agent hasdata or knowledge that is not available to its associated lower-levelmodules.

A non-Socratic classifier module is any classifier module that is not aSocratic agent.

A Socratic controller is a Socratic agent that has a plurality ofassociated lower-level classifier modules and that performs higher-levelpattern classification predicting patterns of comparative behavior ofthe associated lower-level classifier modules. Generally the lower-levelclassifier modules are non-Socratic classifier modules, but in ahierarchical system they may be Socratic agents. Typically, a Socraticcontroller will also manage the joint training of the collection ofassociated lower-level modules, and will manage the process of computinga composite result during recognition. Where the invention is describedin terms of an embodiment as a collection of modules, the embodiment asmodules is to be understood as a description of functionality,regardless of whether implemented in hardware or software and regardlessof whether the hardware or software is organized to into units that aredesignated as “modules.” For example, one embodiment of a Socratic agentis to combine the processing code for collecting evidence for acceptingor rejecting a null hypothesis with the code for the patternclassification in the lower-level module. Regardless of the organizationof implementing software into one or more functions, procedures,subroutines and stand-alone programs, the embodiment of the higher-leveltask of a Socratic agent is to be regarded as functionally ahigher-level classifier module and as an instance of a Socratic agent.As another example, a Socratic controller is associated with a pluralityof lower-level classifier modules. In one embodiment, the plurality oflower-level classifier modules may be implemented as a single body ofcode that controls a plurality of classifiers. This embodiment is to beregarded as a plurality of classifier modules regardless of theorganization of the software into one or more functions, procedures,subroutines or stand-alone programs.

The phrases “higher-level” classifier module and “lower-level”classifier module are relative terms. A recognition system may have manylevels. As a simplified illustrative example, consider a recognitionsystem with only three levels, a “low” level, an “intermediate” level,and a “high” level. In this example, the terms “low,” “intermediate” and“high” are absolute designations for their respective levels. However, aclassifier module in the intermediate level may be a higher-levelclassifier relative to one or more low level modules. The sameintermediate level classifier module may be a lower-level classifierrelative to a particular high level module.

In a broader context, any of several possible relationships mightdetermine that two particular classifier modules have the relationshipthat one is a lower-level classifier relative to the other, which is ahigher-level classifier. For example, in a multi-level optical characterrecognition system the relationship could be based on the length of unitbeing classified, with classifiers of single characters being at a lowerlevel than classifiers of words.

In this document, particularly in discussing Socratic controllers, therelationship of a lower-level classifier to an associated higher-levelclassifier indicates a more specific kind of relationship. Inparticular, if one classifier module sends its classification results asinput to a second classifier, the first classifier is a lower-levelclassifier relative to the second, higher-level classifier. A secondclassifier is also regard as a higher-level classifier if it activelycontrols either the training or the recognition process of a first,lower level process. The second classifier is regarded as activelycontrolling the first if it sends commands to the first classifier. Itis regarded merely as influence, not control, if one classifier sendsdata as input to another classifier, even if the data affects theclassification decision of the second classifier. Finally, a secondclassifier is a higher-level classifier if its classification task is tomodel the behavior of the lower-level classifier, as one embodiment of aSocratic controller may do for its associated lower-level classifiers.

Delayed-decision testing is comparative performance testing by aSocratic agent in which the decision is delayed so that the Socraticagent can measure future comparative performance.

Delayed-decision training is delayed decision testing by a Socraticagent with an associated lower-level classifier module, testing thehypothesis that performance of the lower-level classifier module willimprove if it is trained on a particular training sample with itsassociated label or labels. Delayed-decision training is designed toimprove the robustness over non-Socratic training and to make it moretolerant of labeling errors in the training data.

A linked-model allele is a group of two or more alternate sets of modelscreated by a Socratic agent for delayed-decision testing ordelayed-decision training. In one embodiment, the allele has only twoalternate sets of models and may also be called a paired-model allele.In delayed-decision testing or training, typically only one member ofthe allele is active in the standard recognition process. When theactive allele member makes a contribution to the recognition decision ona particular test item, the recognition computation is redone with othermembers of the allele to determine is there is a performance differenceon that test item. If so, the Socratic agent accumulates evidence of thecomparative performance.

A related classifier module group is the collection of lower-levelclassifier modules managed by a particular Socratic controller.

The invention is described below with reference to drawings. Thesedrawings illustrate certain details of specific embodiments thatimplement the systems and methods and programs of the present invention.However, describing the invention with drawings should not be construedas imposing on the invention any limitations that may be present in thedrawings. The present invention contemplates methods, systems andprogram products on any machine-readable media for accomplishing itsoperations. The embodiments of the present invention may be implementedusing an existing computer processor, or by a special purpose computerprocessor incorporated for this or another purpose or by a hardwiredsystem.

As noted above, embodiments within the scope of the present inventioninclude program products comprising machine-readable media for carryingor having machine-executable instructions or data structures storedthereon. Such machine-readable media can be any available media whichcan be accessed by a general purpose or special purpose computer orother machine with a processor. By way of example, such machine-readablemedia can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, or anyother medium which can be used to carry or store desired program code inthe form of machine-executable instructions or data structures and whichcan be accessed by a general purpose or special purpose computer orother machine with a processor. Thus, any such a connection is properlytermed a machine-readable medium. Combinations of the above are alsoincluded within the scope of machine-readable media. Machine-executableinstructions comprise, for example, instructions and data which cause ageneral purpose computer, special purpose computer, or special purposeprocessing machines to perform a certain function or group of functions.

Embodiments of the invention will be described in the general context ofmethod steps which may be implemented in one embodiment by a programproduct including machine-executable instructions, such as program code,for example in the form of program modules executed by machines innetworked environments. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types.Machine-executable instructions, associated data structures, and programmodules represent examples of program code for executing steps of themethods disclosed herein. The particular sequence of such executableinstructions or associated data structures represent examples ofcorresponding acts for implementing the functions described in suchsteps.

Embodiments of the present invention may be practiced in a networkedenvironment using logical connections to one or more remote computershaving processors. Logical connections may include a local area network(LAN) and a wide area network (WAN) that are presented here by way ofexample and not limitation. Such networking environments are commonplacein office-wide or enterprise-wide computer networks, intranets and theInternet and may use a wide variety of different communicationprotocols. Those skilled in the art will appreciate that such networkcomputing environments will typically encompass many types of computersystem configurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike. Embodiments of the invention may also be practiced in distributedcomputing environments where tasks are performed by local and remoteprocessing devices that are linked (either by hardwired links, wirelesslinks, or by a combination of hardwired or wireless links) through acommunications network. In a distributed computing environment, programmodules may be located in both local and remote memory storage devices.

An exemplary system for implementing the overall system or portions ofthe invention is shown in FIG. 25. This exemplary system include aplurality of general purpose computing devices and memory storage. Byway of example, each computing device could include a processing unit, asystem memory, and a system bus that couples various system componentsincluding the system memory to the processing unit. The system memorymay include read only memory (ROM) and random access memory (RAM). Thecomputer may also include a magnetic hard disk drive for reading fromand writing to a magnetic hard disk, a magnetic disk drive for readingfrom or writing to a removable magnetic disk, and an optical disk drivefor reading from or writing to a removable optical disk such as a CD-ROMor other optical media. The drives and their associated machine-readablemedia provide nonvolatile storage of machine-executable instructions,data structures, program modules and other data for the computer.

Referring now to FIG. 1, there is shown one embodiment of an aspect ofthe invention, showing the relationship between a particular classifiermodule and a particular associated higher-level Socratic agent thatrepresents and acquires knowledge about the first classifier module.

A complex pattern recognition system may have many sources of knowledge.For example, a speech recognition system must have knowledge about thesounds of the language being recognized. Thus, there would be aknowledge source comprising a collection of acoustic models. The systemwould also need to have knowledge about which words are more likely tooccur in given contexts. The system would have some kind of languagemodeling, with one or more knowledge sources based on syntax, semanticsor simply word n-gram frequencies. There would also need to be aknowledge source, like a pronunciation dictionary, associating each wordwith one or more sounds sequences.

Each such knowledge source within a complex pattern recognition systemmay be studied separately. It may be treated as a semi-autonomousmodule, allowing it to be trained and controlled either as a stand-aloneunit or as one module in a multi-module system. As illustrated in FIG.1, this invention introduces the concept of a Socratic agent thatrepresents and acquires knowledge about the performance of a particularknowledge source or classifier module. In a sense, this Socratic agentacquires “knowledge about knowledge.” However, the “knowledge” in thiscase will not be some philosophical abstraction, but will be specificdata structures and parameter values in models and processes used by aclassifier module to recognize the patterns that it classifies. Theknowledge represented by the Socratic agent will be specific datastructures and parameters values derived from specific statistical testsas well as recognition of higher-level patterns.

In normal training of a pattern recognition system, only the trainingdata, block 105, and the classifier module, block 110, are present. Theclassifier module represents the knowledge in the form of one or moremodels with adjustable parameters. In normal training, the knowledgeacquisition comprises adjusting the parameters of the models to optimizea specified objective. In maximum likelihood training, for example, theparameters in the model are adjusted to values which maximize thelikelihood of the models generating the observed training data.

Some embodiments of the invention provide an extra level of knowledgerepresentation and knowledge acquisition, represented by a Socraticagent block 120. Socratic agent block 120 represents knowledge notdirectly about the patterns being recognized by the classifier module ofblock 110, but rather represents knowledge about the patterns ofperformance of the classifier module of block 110. Thus, the knowledgerepresented in block 120 is knowledge about knowledge or Socraticknowledge. The form of the Socratic knowledge in block 120 is notlimiting on the invention. In one embodiment, the Socratic knowledge maytake the form of the Socratic agent 120 learning whether a given modelin a normal classifier module yields better or worse performance resultsas compared to a modified model.

Block 120 provides several capabilities that would be outside the scopeof the non-Socratic classifier module of block 110. In particular, theSocratic knowledge of block 120 interacts with modules from other partsof the overall pattern recognition system, as represented in block 130.Because block 120 represents knowledge about the classifier module 110rather than the pattern knowledge itself, it interacts with othermodules at a more abstract level. By representing Socratic knowledge,block 120 is able to interact with a heterogeneous collection of othermodules that use methodologies that may be completely different from theknowledge representation that is used in block 110.

In one embodiment, block 120 represents and acquires knowledge about thelimitations of the knowledge of block 110. For example, it usestechniques and information outside the scope of block 110 to learn whenthe results computed by block 110 are less reliable. That is, theSocratic agent 120 measures the performance of classifier module 110.There is an analogy to the philosopher Socrates, who tested theknowledge of other Greek philosophers as well as questioning his ownknowledge.

In one embodiment, the Socratic agent 120 acquires knowledge about theknowledge of block 110 by measuring its performance on a set of practiceor validation data 150. In non-Socratic pattern recognition training,each sample of the training data 105 is labeled with what is believed tobe the correct label for each sample in the training data 105. For mosttraining methodologies, it is not necessary to run a recognition processon the training data. However, for certain types of training, arecognition process is run on the training data. For example, incorrective training, a recognition process is run and the parameters ofthe models are adjusted to help correct the errors by improving thescores of the correct label when there is an error or by making theincorrect best-scoring label get a worse score.

Sometimes a separate set of data, practice or validation data 150, isset aside, not to be used for training even though, like training data,the samples are labeled with what are assumed to be correct labels.Typically, in non-Socratic systems the practice data is used to createdevelopment test sets. That is, recognition is run on the practice dataas if it were unknown test data. Because the labels are actually known,the test can be scored automatically to give a preliminary measure ofthe performance of the system while it is still under development.Because the developers of the system may modify the system based on theresults of the development test, the practice data can never again beused as a true, independent test, which is why separate practice datamust be set aside.

For non-Socratic training or development test, it is important that thelabels in the training data or the development test data be as accurateas possible. In the present invention, the practice data 150 is used ina very different way. The present invention is very tolerant of errorsin the labeling of both the practice data 150 and the training data 105.As will be explained in more detail in relation to other Figures, theSocratic agent 120 uses the practice data 150 to acquire Socraticknowledge, that is particular knowledge about the performance of theclassifier module 110. Among other things, this Socratic knowledge canbe used to validate the labeling in the training data 105 and even tocorrect errors in the labeling of the training data.

As in any classifier module, there are two main aspects of the Socraticagent 120, knowledge representation 124 and knowledge acquisition 126(respectively 114 and 116 in the generic classifier module 110). In theSocratic agent 120, block 124 represents knowledge about the knowledgeof the lower-level classifier module 110 and about the credibility andreliability of that knowledge. Other Figures will illustrate severalexamples of different forms of representation of such knowledge. Tounderstand the process shown in FIG. 1, a particular example will beexplained. In this example, the Socratic agent 120 represents knowledgeabout the knowledge of classifier module 110 in the form of statisticalmeasures of the performance of binary alternatives within the structureor models of classifier module 110. The two sets of models correspondingto the two alternatives are called a paired-model allele.

For each such paired-model binary alternative, Socratic agent 120 of theillustrative example forms a null hypothesis and accumulates statisticalevidence to accept or reject that null hypothesis. Such a nullhypothesis is also called a Socratic hypothesis and the Socratic agent120 may be called a paired-model Socratic agent. The null hypothesisstates that the average performance of classifier module 110, accordingto some specified objective function, will be the same for either of thetwo alternatives. As a concrete example, the two alternatives could beto accept or reject the given label for a particular sample in thetraining data 105. If Socratic agent 120 successfully rejects anincorrect label in the training data 105, the labeling error can becorrected.

Higher-level Socratic agent 120 controls block 140 to obtain andannotate practice data that will be used to accumulate statistics tosuccessfully accept or reject a null hypothesis such as described above.Typically, labeling or annotation of training data or practice data isdone manually by human labor, and may be very expensive if a largeamount of data is to be used. The present invention is much moretolerant of labeling errors in the practice data and can use lessexpensive methods for acquiring the practice data. For example,automatic labeling may be used to label the practice data. As will beexplained in more detail in relation to other Figures, the automaticlabeling can use the recognition process for which the classifier module110 is being trained, if that overall recognition process is a multipleclassifier module process with one or more other sources of knowledgethat are complementary to knowledge in classifier module 110. Forexample, in a speech recognition system in which classifier module 110is acquiring knowledge about acoustic models for individual sounds, acomplementary knowledge source would be a language model with knowledgeabout the relative likelihood of different word sequences. Similarly, ifclassifier module 110 is acquiring knowledge about the patterns ofcharacters in an optical character recognition system, knowledge aboutwords and words sequences would be complementary sources of knowledge.In FIG. 1, these complementary classifier modules and sources ofknowledge are represented in block 160.

Block 150 presents a given selection of practice data to classifiermodule 110 and Socratic agent 120 causes classifier module 110 toperform recognition or classification on the given data. Socratic agent120 coordinates with other parts of the system 160, so that theevaluation 130 of the performance of classifier module 110 is performedrelative to an objective function that may be based on the endperformance of the overall system, not just classifier module 110 inisolation.

In the particular example of a paired-model Socratic hypothesis, Block130 accumulates statistics about the comparative performance of the twoalternative model sets, with the performance evaluated in the context ofall of the knowledge supplied by other parts of the system. Sequentialdecision theory statistics are accumulated to reject the null hypothesisif and only if the performance of one of the two alternatives is betterby an amount that is statistically significant at the specified level ofsignificance. Errors in the labeling of the practice data will noteffect the statistic decision so long as the labeling errors areunbiased between the two alternatives of the paired-model sets.

In one embodiment, this Socratic agent will begin with the hypothesisthat the lower level classifier module has no true knowledge until it isspecifically proven otherwise.

A Socratic agent is an active process of acquisition of knowledge aboutan associated classifier module, not a mere repository of knowledge. Theprocesses of Socratic agents will be explained in more detail inreference to FIGS. 3, 4, 5 and 6. An illustrative example will bediscussed following FIG. 4.

FIG. 2 shows the same components and relationships as FIG. 1. Inaddition, FIG. 2 illustrates the fact that a single lower-levelclassifier module 110 may have many semi-autonomous Socratic agentsactive simultaneously, each representing and acquiring Socraticknowledge about different pieces of the knowledge within the lower-levelclassifier module 110. In FIG. 2, it is to be understood that theinvention may have an arbitrarily high number of such Socratic agents120 associated with each lower-level classifier module 110, not just thethree illustrated. It is also to be understood that the dangling arrowsleaving each of the Socratic agents 120 connect to the blocks 110, 130and 140 respectively. These other Socratic agents may reside on the samesystem or may be distributed across a network. In one embodiment,Socratic agents on other systems distributed across a network will havetheir own instances of block 130 and 140. However, since some knowledgemay also be shared across multiple system, as shown in FIGS. 21 and 22,in one embodiment Socratic agents on separate systems may also share adistributed implementation of blocks 130 and 140.

FIG. 3 illustrates a process, based on Socratic agents, of knowledgeacquisition that is robust against mislabeling in the training data (aswell as other sources of variability) and is even robust against a highrate of errors in the evaluation or practice data.

A distinguishing feature of a Socratic agent is that the Socratic agentmakes use of data or knowledge that is not available to the system,subsystem, module or model with which the Socratic agent is associatedeither not available at the current time or not available because thedata is coming from another system or subsystem. One example of suchknowledge is illustrated in FIG. 3. In the process shown in FIG. 3, theSocratic agent delays a decision and uses the knowledge of the futureperformance of the associated model.

In an online or real-time pattern recognition application, suchknowledge is not available during a given recognition task. The answerto the current problem must be given more or less immediately beforeproceeding to the next problem. In such a case, neither the answer noran associated (non-Socratic) confidence measurement may be indefinitelypostponed. However, the Socratic agent illustrated in FIG. 3 operatesdifferently and does indefinitely postpone the decision as to whether ornot the current training sample and its associated label should be usedto train or update the model or module with which the Socratic agent isassociated.

Referring now to FIG. 3, in block 301 a training sample is obtained. Atraining sample includes a data item and an associated label. A largecomplex pattern recognition system may require a large quantity of suchtraining samples. However, it can be very expensive to have humans labelsuch a large quantity of data or to have humans check the labeling thatmight be available from a less expensive source. Therefore, thisinvention is designed to be tolerant of errors in the labels associatedwith the training samples. It is also tolerant of variability in thedata associated with the training sample. Therefore, for the trainingsample obtained in block 301 it is not assumed that the label isnecessarily correct and it is not assumed, even if the label is correct,that the associated data is typical of the population represented by themodel associated with the label. The invention views these assumptionsas hypotheses to be tested, not as known facts.

In block 302, a copy of the current model or module being trained issaved unchanged and a second, modified copy is also saved after beingtrained on the training sample obtained in block 301. Typically, aclassifier module will represent knowledge as a set of models. If thechange in the knowledge representation caused by training on aparticular sample is limited to a single model, then only that modelneeds to be duplicated. If the change is distributed throughout theknowledge representation of the classifier module, then a set of modelsor the entire module may need to be duplicated.

These two versions of the model or module are linked so that in futuresteps of the process both versions of the model or module are availableand statistics may be obtained on their comparative performance. Thislinked pair of models or modules is called an allele. Associated withthis allele is a particular statistical hypothesis, called the nullhypothesis. The null hypothesis states that the average performance ofthe two linked models is the same. The later blocks of FIG. 3 will beperforming a statistical sequential decision process deciding whetherthe null hypothesis can be rejected. The performance measurement may beany appropriate performance measurement that may be computed as if thegiven labels for the practice data are the correct labels. In theillustrated embodiment, however, the invention is actually very tolerantof errors in these labels of the practice data.

In one embodiment, the performance measure is simply the average errorrate on the given classification task. However, when the classifiermodule being training is a component of a larger recognition system, inanother embodiment the performance measure is the average error rate ofthe larger recognition system at the end of the complete recognitionprocess, rather than the average error rate of the classifier module byitself. Depending on the system design, in other embodiments otherperformance measures may be used. For example, when the particularclassifier module being evaluated is a early component in multi-stagerecognition process, the performance measure may be the percentage ofinstances in which the correct answer is passed on to the next stage ofrecognition given resource constraints, rather than the percentage oftime that the early component module gives the correct classification asits first choice.

An important property to note is that the invention in the embodimentillustrated in FIG. 3, does not require that the correct labels be knownfor the practice data. No decision is made and no model is trained orupdated based on the single item of practice data, whether or not itslabel is correct. Rather, the process illustrated in FIG. 3 graduallyaccumulates evidence and the process terminates and takes action only ifeventually sufficient evidence can be accumulated to reject the nullhypothesis. Even a substantial fraction of mislabeled practice data willnot effect the probability of falsely rejecting the null hypothesis ifthe labeling errors are unbiased relative to the two paired models.

In block 303, the data sample obtained in block 301 is compared with thecurrent model, that is the model before any adaptive or other trainingbased on the given data sample. If the data sample is very differentfrom the current model, it is considered to be an outlier. The degree ofdifference for a sample to be considered an outlier is an empiricallyadjusted control parameter. This parameter, and other controlparameters, may be empirically adjusted by the process illustrated inFIG. 16.

If it is determined that a training sample is an outlier, it is notrejected for training. Instead, block 304 creates a new model, which istested by the process illustrated in FIG. 4. In addition, training alsocontinues with block 305. This training process is tolerant of outliersas well as mislabels in the training sample. Training on outliersincreases the robustness of the model or module to similar variabilityin future data items.

Continuing in reference to FIG. 3, block 305 begins a loop that isrepeated many times until enough evaluation data pertaining to theallele has been obtained. In the illustrated embodiment, the data thatis used to evaluate the null hypothesis is either new practice data thatis obtained in the future after the Socratic agent has been created, orit is practice data (separate from the training data) that has been setaside. Thus, it may be called either practice data or evaluation data.

Block 306 obtains an estimated answer or label for the evaluation dataobtained in block 305. In prior art pattern recognition methods, theevaluation data usually must be hand labeled and very carefully checked.As stated before, this process of hand labeling and checking can be veryexpensive for a large quantity of data. However, as already mentioned,this invention tolerates a very high error rate in the labeling of itsevaluation or practice data if certain reasonable conditions are met.This is in addition to the tolerance of mislabels in the trainingsample. The two kinds of tolerance occur for different reasons. Becauseof this error tolerance, block 306 may use labels or estimated answersthat have been obtained by automatic processing rather than handlabeling. Hence it is practical to obtain a large quantity of evaluationdata at reasonable expense, so the process may loop through block 305many times.

Block 307 accumulates performance statistics based on the evaluationdata and the estimated answer. These performance statistics will not tryto measure the absolute performance of the pattern recognition system,which is one of the reasons that it is not essential to hand label andcheck the evaluation data. Rather, these performance statistics willonly measure the comparative performance of the two, paired versions ofthe models in the allele. Note that a wrong label will tend to notaffect the null hypothesis, as it is equally likely to favor eithermodel in the allele, provided the wrong label in the practice data wasgenerated by an independent system, i.e., not the model under test. Ifthe classifier module being trained is a component of a larger system,in one embodiment the Socratic agent is environment-aware as well asself-aware. That is, the comparative performance is not measured inisolation but rather in the context of the surrounding system. Forexample, if the module is a component module in a collection ofcooperating modules, the measurement will be based on whether or notthere is a difference in the combined result of the whole collection,depending on which of the paired versions in the allele is used.

Block 308 tests whether the accumulated performance difference betweenthe two, paired model versions is statistically significant according tosequential decision theory. For example, sequential decision theorymight determine that a performance difference is statisticallysignificant if the probability of rejecting the null hypothesis bychance is less than 0.01. Compared to simple hypothesis testing,sequential decision theory can decide to postpone a decision and waituntil more data has been accumulated. Sequential decision theory is wellknown to those skilled in the art of statistics. Even if the evaluationlabels have a high error rate, if the null hypothesis is true for theportion of the evaluation data that is mislabeled, then the decision toreject the null hypothesis will merely be postponed until eventuallyenough data is accumulated to reject the null hypothesis in favor of thebetter model version.

If it is available, block 308 will use a human-supplied orhuman-verified answer. However, if a human-supplied or verified label isnot available, block 308 obtains an automatically generated label.Preferably, the automatically generated label will be generated by asystem that includes additional sources of knowledge beyond theclassifier module being tested. For example, in a speech recognitionsystem, if the classifier module being evaluated is a collection ofacoustic models, the automatically generated label may be generated by acomplete system that includes a language model. In a multi-stage systemin which the given module attempts to approximate a higher-stage module,preferably the automatically generated labels may be generated by thatlater stage module. Since in such a case the task for the given moduleis to approximate the later-stage module, the label generated by thelater-stage module is by fiat the “correct” answer.

If the evaluation data is labeled with an automatic recognition processthat includes the classifier module being trained, in one embodiment theactive version in the given allele is set to be the version that, at thecurrent point in the evaluation, is the worse performing of the twoversions even though the difference is not yet significant. Thisprevents an accumulation of bias in favor of the current favorite. Themodel is switched between the two versions whenever the preferencechanges.

If the accumulated performance statistics are sufficient to reject thenull hypothesis, then one of the model versions performs significantlybetter statistically than the other. Therefore the process proceeds toblock 309 at which the better model is selected and the testing of thisparticular allele is terminated. Control then proceeds to block 311.

Block 311 marks the training sample with the selected best performinglabel. If the null hypothesis has been rejected in favor of the modelversion that has been trained on the given training sample, then theassociated label for the training sample is marked as reliable. If thenull hypothesis has been rejected in favor of the model version that hasnot been trained on the given training sample, then the associated labelis marked as unreliable. Thus, a module with a Socratic agent asillustrated in FIG. 3, will not only be self-aware andsystem-environment-aware, but will also self-correct the presentedtraining samples. In one embodiment, the training sample is alsoannotated with all or a portion of the information that has beengathered in the process of evaluating the null hypothesis or a summarythereof. In this embodiment, this additional information will be storedfor possible use in subsequent analysis.

If the accumulated performance statistics are not yet sufficient toreject the null hypothesis, the process proceeds from block 309 to block310. Block 310 tests a stopping criterion based on how much evaluationdata has been accumulated so far without the null hypothesis beingrejected and the relative availability of system resources to be testingsuch model pair alleles. The system may have created and be testing manysuch pairs simultaneously. However, if there is no shortage ofresources, the testing of a given allele may continue indefinitely. Withlimited resources, block 310 may decide to stop testing of thisparticular allele based on a control parameter that may be empiricallydetermined as shown in FIG. 16. If block 310 stops the testing processwithout the null hypothesis being rejected, it is somewhat arbitrarywhich model version is selected because the performance difference isnot statistically significant. The selection could be made at random.For definiteness, FIG. 3 illustrates the embodiment in which the betterperforming of the two models is selected.

If the stopping criterion has not been met, which will usually be thecase, the process returns to block 305 to continue accumulating moreevaluation data that uses the models in the allele.

The process illustrated in FIG. 3 represents a kind of “delayeddecision.” The decision as to whether or not the training sample is agood sample is not based on the information available at the time thetraining sample is encountered. The decision is based on the actualobserved (future) performance of the system on an accumulation ofevaluation data. Furthermore, the decision is delayed until astatistically significant amount of evidence has been accumulated. Theprocess is tolerant of errors in the labeling of the evaluation data aslong as the null hypothesis is true for the portion of the evaluationdata that is mislabeled. The process is self-aware such that it is notonly tolerant of errors in the training sample, but also it can markthose errors in block 311, producing better labeled training data forother training.

Because there may be a substantial delay before a decision is reached toreject the null hypothesis or otherwise stop the process, more trainingsamples for the particular model or module may be encountered. If so, anew allele may be created for each of them, so that a substantialplurality of Socratic agents may be operating at a given time.

In summary, the creation and operation of the Socratic agent illustratedin FIG. 3 causes the following steps to be performed:

-   -   1) creating the Socratic agent (block 302) creates an electronic        linkage among the different instances of the model obtained from        training on or skipping the given training sample;    -   2) in the embodiment illustrated in FIG. 3, the Socratic agent        creates a null hypothesis between the linked pair of models;    -   3) in this embodiment, the Socratic agent accumulates        measurements of comparative performance in order to accept or        reject the null hypothesis (block 307,308);    -   4) the accumulated evidence is transmitted back to select the        better model (block 309) and to annotate the training sample        (311);    -   5) if the null hypothesis is rejected, then the better        performing model becomes the active model for subsequent        recognition and subsequent training uses or skips the given        training sample as indicated.

Notice that these steps apply to any form of trained patternrecognition, not just to one application. Note further that no decisionis made based on a single evaluation sample taken from the practicedata. Indeed, no selection is made of the better model nor is anyannotation information transmitted back to mark the training sampleunless and until sufficient evidence has been accumulated to reject thenull hypothesis at a statistically significant level.

By way of example, consider an optical character (OCR) recognitionsystem. For the illustrative example, assume that the OCR system is amulti-stage recognition system including a low-level classifier modulethat matches the observed data features from the two-dimensional arrayof pixels from the optical image to models for the characters, and ahigher-level module that models the sequences of characters in terms ofword and word sequences. Assume that the models being trained are themodels of the pixel patterns in the low-level classifier module. Supposethat a particular character in the training data is smudged. Should thesmudged character be used in the training? It is difficult to decideinitially. If the smudge makes the character look more like some othercharacter than like the actual character underneath the smudge, thenincluding this particular sample in the training could degrade the modelfor the actual character and make the model falsely accept instances ofthe other character that looks like the modeled character as smudged.For example, if an instance of the letter “o” is smudged so that itlooks like only part of a circle with a smudge to the right, it mightlook like the letter “c”. On the other hand, if such smudges are commonand will occur frequently in the data to be recognized, the models mustsomehow be trained to expect such phenomena. It is difficult to decidewhich choice will work better merely by examining the smudged character,even with the advice of a human expert much less fully automatically.

However, continuing the illustrative example based on one embodiment ofFIG. 3, the decision is not to be made merely by looking at the smudgedcharacter. Instead, a Socratic agent is created with a linked pair ofmodels and a null hypothesis is formulated between the linked pair. Onemember of the pair of models is created by skipping the particulartraining sample comprising the smudged character. The other member ofthe pair of linked models is created by training on the smudgedcharacter. Note that the system does not need to know that theparticular training sample is smudged. The same operation can beperformed on any training samples. The assumption that the character issmudged is merely part of the illustrative example so that the behaviorof the recognition system upon training on the particular sample may beunderstood.

The system continues on in its normal operation. In the illustrativeexample, assume that there is no special set aside practice data, butrather the recognition data that is subsequently encountered by thesystem is used as practice data for the purpose of finding samples forevaluating the comparative performance of the linked models and foraccumulating evidence to accept or reject the null hypothesis. In thissubsequent recognition process at any one time only one of the pair oflinked models is active. In a complex recognition system, not everymodel participates in a particular recognition decision. Only the modelsfor the best matching class and the models for the close scoringalternatives matter in the recognition of a particular sample. Wheneverthe active member of the linked pair of models so participates in arecognition decision, the linkage tells the system to take specialaction if changing which member of the linked pair is active mightchange the recognition result. The system replaces the active member ofthe linked pair of models with the other model and rescores therecognition. If the rescoring results in choosing a different class asthe best scoring class, then there is a difference in performancebetween the two linked models and comparative performance statistics areaccumulated.

Note an important property of the one embodiment illustrated in theexample. Note only is the decision of whether to train on the particulartraining sample, which for purpose of the example has been assumed to besmudged, not made just by examining the smudged sample itself, thedecision is not made by a looking at a single practice or evaluationsample. In some embodiments, the decision is only made afteraccumulating statistically significant evidence.

Given the null hypothesis, the average performance of the two linkedmodels is the same. Therefore, if there is a difference in performanceon a particular evaluation sample taken from the practice data, eitherof the linked models is equally likely to be the one that performsbetter on the particular sample. Since there are only two alternatives,that means that the probability that either particular model is the onethat performs better is exactly 0.5. Under the null hypothesis, for anyother evaluation sample the probability for either model performingbetter is again 0.5 and the choice of which model performs better on agiven evaluation sample is made independently. As a specific example ofpossible evaluation results, suppose that the same model performs betteron the first six evaluation trials. Because the probability is 0.5 foreach trial, the same model could perform better just by chance with aprobability of (0.5)⁶= 1/64=0.015625. That is, the probability isgreater than 0.01, and the statistic would still not be significant atthe 0.01 level.

This example also illustrates another aspect of one embodiment. In theexample, the practice data may be taken from the subsequent regular useof the recognition system. In such regular use there may be feedback inthe form of a user correcting any errors that are made by therecognition system. If such error correction feedback is available oneembodiment of the invention will make use of such information. However,if such information is not available, one embodiment of the inventionstill operates as shown in FIG. 3. In this case the practice data ismerely labeled automatically by the recognition system.

Note that the labeling of the practice data is done by the wholerecognition system, not just by the classifier module being trained. Inthe illustrative example, that means that the automatic labeling alsomakes use of the knowledge of the words and word sequences that isavailable in the overall recognition system. The knowledge that onlycertain character sequences form words, and the knowledge of which wordsare more likely, helps the system fix many of the errors that would bemade by the lower-level character classifier model operating by itself.However, a minority fraction of the time the application of theknowledge of the words and word sequence may introduce an error. Forexample, if an ambiguous character occurs in a less common word, theoverall recognition system may choose a more common word with adifferent character, even though the lower-level character classifiermodule operating by itself might have chosen the correct character. Inone embodiment shown in FIG. 3 and illustrated by this example theseerrors introduced by the overall recognition process do not cause theprocess to fail. The process does not depend on the correct labeling ofany one practice sample. The process only requires that the errors atleast average out so that the statistical significance of the test ofthe null hypothesis is not destroyed.

In the particular illustrative example, all that is required is that,when the overall system introduces an error, the probabilitydistributions of errors not be biased in favor of one or the other ofthe linked models. That is, if the word or word sequence knowledgecauses the overall system to make an error, the null hypothesis shouldbe true for data restricted to the errors. Given that such an error hasbeen made, either of the two linked models should be equally likely toperform better over a significant plurality of samples. In theillustrative example, the difference in the two linked models comes fromtraining on or skipping a particular training sample, which has beenassumed to be smudged. Since the presence of a particular kind of smudgeis completely independent of identity of the words and the wordsequence, in the example the conditions should be satisfied such thatthe null hypothesis test should remain valid. The derivation that thenull hypothesis test is valid is not based on any assumption that theerror rate in the automatically labeling is low or that it is less thanany particular value. Essentially the process will work with anarbitrarily high error rate in the automatic labels as long as there isno bias created between the linked models as a result of these errors. Adifferent aspect of this question will be considered in a laterillustrative example.

As a final step in the illustrative example, assume that eventually thenull hypothesis is rejected in favor of the model for which training isperformed on the smudged sample. Then, the training sample is marked asreliable and this better model is made part of the standard version ofthe character classifier module. In particular, as further training isperformed that includes particular smudged training sample, thattraining will include the particular smudged sample as labeled. However,if the null hypothesis had been rejected in favor of the model thatskipped that particular training sample, then in subsequent training theannotation on the particular training sample would tell other trainingprocesses to also skip that particular sample with the smudge.

In one embodiment, to be discussed in more detail in reference to FIG.23, the allele contains models not merely obtained from training on thegiven training sample as labeled, but also models based on training onthe given training sample with alternate labels. In the example, assumethat the character classification module in the OCR system not onlyreports the best matching character classes, but also the identity ofany other character class that matches nearly as well as the best. Thenthe process shown in FIG. 3 may be modified to set up a null hypothesisthat hypothesizes that the performance of all the alternate models isthe same. When this null hypothesis is rejected, then the alternatemodel is associated with a particular alternate label for the particulartraining sample if those that alternate label yields a betterperformance. In this case, block 311 marks the training sample with thisnew label that performs better at a statistically significant level.

Following FIG. 4, some further comments will be made referring to thisexample.

With reference to FIG. 4, consider a new model or module that wascreated by block 304 in FIG. 3. Such a model or module may be tested asillustrated in FIG. 4. In this case, the Socratic agent is responsiblefor acquiring the knowledge as to whether the new model increasesperformance by an amount sufficient to make up for the resources that itrequires. The process of FIG. 4 may also be used to test the value of anexisting model or modules.

To make the process easier to understand, it will be explained withreference to an example taken from speech recognition, but the sameprinciples will apply to any kind of pattern recognition. When a speakersays a word with a pronunciation that is very different from anypronunciation for that word currently in the dictionary, a decision mustbe made as to whether to add a new pronunciation to the dictionary thatmatches this particular instance.

There are several things that could go wrong when a new pronunciation isadded to the dictionary. If either the script is wrong or if the speakermisspoke, the actual word spoken may be a different word from the wordin the script. Adding an instance of that other word as a pronunciationfor the script word would mean that future instances of the other wordwill match the pronunciation and sometimes be incorrectly recognized asthe script word. Even if the script is correct, the particular instancemay be an unusual pronunciation. In many speech recognition systems,once a pronunciation is in the dictionary there is no way ofrepresenting that it is very rare, or that it only occurs in certaincontexts. Even if the pronunciation is common and ought to have beenincluded in the dictionary, deducing the correct representation of thepronunciation in terms of units of sound such as phonemes is anerror-prone process, especially when done from a single instance. Addinga pronunciation to the dictionary in which there are errors in thephonemes may make the performance worse. On the other hand, leaving avalid pronunciation out of the dictionary will cause the system torepeat the same mistake over and over.

It is impossible just from measuring how well the particular instancematches the existing pronunciation to decide whether or not the instanceis a valid pronunciation that should be included in the dictionary.Valid variations in pronunciation may be as great as the differencebetween two words. For example, the acronym AAAS may have the dictionarypronunciation “AY AY AY ESSE.” However, a speaker may instead say“triple AY ESSE.” We can see from understanding the nature of the letterstring that the new pronunciation is reasonable, that is, it is likelyto occur again, and that it should be in the dictionary. Acoustically,however, it is as different as a completely different word. In fact, itactually is a different phrase, with the two words “AY AY” replaced bythe word “triple.”

The Socratic agent, however, does not need to make a decision just basedon the sounds in the current instance and how well it matches or howmuch it fails to match the existing models. Instead, it delays thedecision and makes the decision based on whether the system performanceimproves across a series of evaluation data samples if the pronunciationis added. The same principles apply in deciding whether to add any newmodel to any pattern recognition system.

Returning now to FIG. 4, block 401 obtains a training sample that is acandidate for creating a new model. For example, this training samplecould be a training sample from block 304 of FIG. 3 that was detected asan outlier by block 303. Generally the new model will be part of aparticular subsystem or module within a larger system. The assignment ofthe model to a module will be determined by the kind of unit beingmodeled. For example, in a speech recognition system the unit may be aphoneme, a syllable, or a word. In a handwriting recognition system, theunit may be a stroke, a letter or a word. The evaluation illustrated byFIG. 4 will be an evaluation of the performance of this module. Thisperformance evaluation may be fully supervised with human-supplied orhuman-verified labels, or may be semi-supervised by labels automaticallygenerated by the larger system of which the module is a part.

Block 411 creates a one-shot model from the training sample obtained inblock 401. A one-shot model is one built, at least initially, from asingle example. Block 411 may use any method of model building that iscapable of one-shot learning. The new model may be, but is not requiredto be, of the same kind as are built by the recognition system in itsstandard training from multiple examples. Block 411 may also usemodel-building techniques that are specifically designed for one-shotlearning.

It may be possible to represent the unit being modeled as a sequence ofsubunits. For example, a word in a speech recognition system may berepresented as a sequence of phonemes. In a handwriting recognitionsystem or an optical character recognition system, a word may berepresented as a sequence of letters. In such a case, in one embodimentrecognition of the sequence of unknown subunits is performed, usingexisting models for the subunits, and taking into account statistics ofrelative likelihood of different sequences of subunits and anyadditional information that might be available, such as the spelling ofthe word in speech recognition. The examples of the subunit that occurwithin the data sample may be used as training samples for theirrespective subunit labels, preferably using a robust procedure such asillustrated in FIG. 3.

Another method of one-shot learning that may be used in block 411 is touse a network with multivariate Gaussian distributions associated withthe nodes. If the data is a stream of data frames, and if the featureattributes of the unit to be modeled may vary as a function of timewithin the data sample, the unit is represented as a simple network thatis a sequence of nodes, each node (except the first) connected with theprevious node and each node (except the last) is connected with thefollowing node. If the features of the unit are to be modeled as notvarying as a function of time, then the unit may be represented as asingle node. If the unit is represented by a network with more than onenode, the network may be segmented and time aligned with the data sampleusing dynamic programming as shown in the following pseudo-code. Thedistance function D(t1,t2) may be the Euclidean distance or any otherdistance function defined on the vector space of data features.

Pseudo-code for segmenting and time aligning a sample to a network withN nodes

For time t1 going from the beginning of the sample T0 to the end of thesample Tend   For time t2 from T0 to Tend     Compute M(t1,t2), the meanof the feature vectors from t1 to t2.     Compute D(t1,t2), the summeddeviation from the     mean from t1 to t2 For time t from T0 to Tend  Score(1,t) = D(T0,t)   For node n going down from N to 2    BestSegTime(n,t) = t     BestSegScore = Score(n−1,t−1)     For timet1 from t−1 down to T0       SegScore = Score(n−1,t1−1) + D(t1,t)      If (SegScore<BestSegScore) then         BestSegScore = SegScore        BestSegTime(n,t) = t1     Score(n,t) = BestSegScore Set node n =N, time t = Tend While (n>1) do   SegmentTime(n) = BestSegTime(n,t)  Time t = SegmentTime(n)   Node n = n −1 SegmentTime(n) is thebeginning time of the n th segment, which is aligned to the n th node.

Once the data sample has been segmented and aligned to the network, amultivariate Gaussian model is created for each node. The mean vectorfor the Gaussian for a given node is the sample mean of the time framesaligned to the node. The covariance matrix is taken to be a diagonalmatrix and the variance vector is estimated by an empirical Bayesprocedure, well known to those skilled in the art of statistics, basedon the sample variance and the model variance for sounds similar to thesound aligned to the given node.

Block 402 builds an allele representing the two alternatives. In thiscase, however, the alternatives are asymmetric. One alternative is tonot create (or not retain) the new model (or an existing model obtainedin block 421). However, if the (new) model is retained permanently, itwill take up resources, that is, memory to hold the model andcomputation whenever the model must be matched against incoming data.

Block 403 estimates the marginal of the resources that would be used ifthe model were made permanent. This marginal cost estimate controls therate at which new models are added to the system. In one embodiment, themarginal cost is computed as the product of a constant times theadditional amount of computation time required to do a patternclassification with the additional model. In another embodiment, theconstant is replaced by a variable parameter that can be adjusted tocontrol the rate at which new models are added to the system. Ifresources become scarce, then the marginal cost is made very high(increased toward infinity) to prevent the system from running out ofresources. If the marginal cost is high then very few new models will beable to increase the performance by an amount greater than the marginalcost for a statistically significant number of practice samples. Thus,in this situation few new models will be accepted, which is desirable ina situation in which resources are becoming scarce. If resources are notscarce, the marginal cost is nominal, and the constant can instead beused as a control parameter, which may be empirically tuned by theprocedure shown in FIG. 16.

In a system with multiple redundant models, the contribution of a givenexisting model may drop below its marginal cost. In such a system,existing models may be obtained by block 421 and tested in the samemanner as new models. An existing model may be volunteered to block 421by the model's Socratic agent or a model may be selected at random at arate controlled by an empirically tuned parameter.

Whatever the source of the model being tested, block 404 begins anevaluation loop. This evaluation loop is similar to the evaluation loopin FIG. 3, but the null hypothesis is being tested against a one-sidedalternative. That is, to reject the null hypothesis the evidence mustshow that performance with the given model is significantly better thanwithout the model by at least an amount determined by the marginal cost.The one-sided test with margin means that the test will be somewhatrobust against bias in the evaluation data. On the other hand, with themargin some models will be rejected even though they make a smallimprovement in performance. Furthermore, a higher error rate in theevaluation data may cause additional models to be rejected because theaccumulated performance statistics have higher variance and fail toreach the margin threshold. Thus, the evaluation loop in FIG. 4 isconservative in its acceptance of new models in order to remain robustagainst errors in the evaluation data.

Block 404 obtains an evaluation sample.

Block 405 obtains an estimated answer. If it is available, block 405will use a human-supplied or human-verified answer. However, if ahuman-supplied or verified label is not available, block 405 obtains anautomatically generated label. Preferably, the automatically generatedlabel will be generated by a system that includes additional modules orsources of knowledge beyond the module being tested. For example, in aspeech recognition system, if the module being evaluated is a collectionof acoustic models, the automatically generated label may be generatedby a complete system that includes a language model. In a multi-stagesystem in which the given module attempts to approximate a higher-stagemodule, preferably that higher-stage module will generate theautomatically generated labels. Since the task for the given module isto approximate the higher-stage module, the label generated by thehigher-stage module is by fiat the “correct” answer.

Block 406 computes two answers for the module being tested: one withoutthe given model being tested and one with the given model. These answersare compared with the estimated answer obtained in block 405. Theperformance on this evaluation sample is then accumulated with theperformance statistics previously accumulated in previous iterationsthrough this evaluation loop.

Block 407 checks to see if enough evidence has been accumulated toreject the hypothesis that the new model fails to improve performance bythe specified margin. FIG. 3 tested two models, so the null hypothesiscould be rejected in favor of either model. This is called a two-sidedtest of the null hypothesis. FIG. 4, however, is comparing theperformance with an extra model or element to the performance withoutthat model or element. The extra model or element requires additionalresource, as estimated by the marginal cost. If not enough evidence hasbeen accumulated to reject the null hypothesis than the additional modelor element will not be accepted. Furthermore, if the performance withthe additional model or element is not enough better than theperformance without the additional model or element, then the additionalmodel or element will not be accepted whether or not the null hypothesiscould have been rejected. Thus, it is only necessary to see whether thenull hypothesis could be rejected because there is statisticallysignificant evidence that the system with the additional model orelement performs better than without by an amount greater than themarginal cost. This is called a one-sided test of the null hypothesis,which is a form of hypothesis testing well known to those skilled in theart of statistics.

If the hypothesis is rejected, the process proceeds to block 408 atwhich the new model is made permanent, or the existing model or moduleunder test is retained.

If the hypothesis is not rejected, then the process proceeds to block409 at which a stopping criterion is checked. If the hypothesis has notyet been rejected by the time the stopping criterion is met, the modelbeing tested is judged as not contributing to improved performance bymore than its marginal cost. The process then proceeds to block 410 andthe model is deleted.

If the stopping criterion has not been met, then the process returns toblock 404 to gather more evidence.

Socratic agents and the processes of FIGS. 3 and 4 may be furtherunderstood by consideration of the following illustrative example. Thisexample should be construed only as an example and not as imposing onthe invention any limitation that may be present in the illustrativeexamples. FIG. 5 presents the broad concept of delayed-decision testing.FIGS. 3 and 4 are instances of a particular form of delayed-decisiontesting, namely delayed-decision training.

For an illustrative example, consider a speech recognition system inwhich the training data was automatically labeled, so there are anon-negligible number of label errors in the training data. For theexample, assume that a particular training sample is actually the word“fog,” but has been mislabeled as “frog.” Following the process of FIG.3, this particular training sample would be obtained in block 301. Thena linked-model Socratic agent is created in block 302. This Socraticagent saves of copy of the pre-existing acoustic models, that is, theacoustic models from before this training sample was encountered. Ifthere is an on-going training process, then these pre-existing modelswill not be frozen but rather will continued to be trained with theparticular training sample skipped. The Socratic agent also creates aset of models that includes this particular wrong training sample. Thatis, the Socratic agent creates a set of models in which this trainingsample is used with the label “frog.”

Under the assumption of the illustrative example, the nominal label“frog” is incorrect, but that fact is not known at this stage to theSocratic agent or to the training process in which it is participating.The Socratic agent would create the same two sets of models if thenominal label of “frog” were correct. The differences between the twosituations will only show up under the future testing.

In the illustrative example of speech recognition, there will actuallybe several linked models that will be different under the two conditionsof whether or not the particular training sample is skipped. A complex,state-of-the-art speech recognition system may model the acoustics atseveral levels, incorporating varying amounts of context into themodeling. In particular example, not only might there be an acousticmodel for the word “frog,” there would probably be models for each ofthe phonemes in the word “frog.” That is, there would be acoustic modelsfor /f/, /r//, /aw/, and /g/. There may be acoustic models for thephonemes that might be dependent on the context of surrounding phonemes.For purposes of the illustrative example, assume that the system has aacoustic model for the whole word “frog,” a context-independent ancoustic model for each of the phonemes and a context dependent model foreach phoneme given the context of one phoneme on each side.

Block 303 tests the particular training sample to see if it is anoutlier relative to the current models. Because the training sample isactually an instance of the word “fog,” but is labeled as “frog,” it islikely to be labeled as a potential outlier for one or more of themodels. For purposes of the example, assume that the particular trainingsample is considered to be an outlier for the whole word model for theword “frog” and is also considered to be a potential outlier for boththe context-independent model and the context-dependent model for thephoneme /r/, since no actual /r/ sound exists in the given trainingsample.

However, the process of FIG. 3 does not reject training samples merelybecause it appears that they might be outliers. In either case, itcontinues with the process of FIG. 3. However, for the models for whichthe sample is likely to be an outlier, the process also goes to block304, which creates a new model and tests it using the process of FIG. 4.To summarize what has happened so far in the example, a Socratic agenthas been created for testing each of the acoustic models that isaffected by training on the given training sample. Each Socratic agenthas a pair of linked models in which one member of the pair is trainedon the particular sample and one member of the pair skips training onthe particular sample. In addition, for several of the word “frog” andthe phoneme /r/, new models have been created to be tested by theprocess of FIG. 4.

In FIG. 3 and in FIG. 4, the corresponding Socratic agent for each ofthe linked model pairs creates a null hypothesis that states that theperformance will be the same (at least on average) for the two linkedmodels. Continue following the example to see how the evaluationproceeds.

Block 305 (or block 404 of FIG. 4) obtains an evaluation sample. Thisevaluation sample is obtained from practice data, e.g., data for whichputative labels are available just as for training data, but the data isused for recognition rather than for training. As practice data, it maybe used for development and tuning of the recognition system. In theillustrated embodiment of the invention, it will be used for evaluationof the null hypotheses of the Socratic agents.

Block 306 (or block 405 of FIG. 4) obtains the estimated answer for theevaluation sample obtained in block 305. For the example, assume thatthe practice data is actually data obtained from on-going operation ofthe recognition system. That is, it is new data that is sent to therecognition system to be recognized and it has no human-supplied labels.The recognition process generates a set of labels as part of its normaloperations. This data becomes practice data simply because theseautomatically generated labels are used the same as if there were labelsthat were known to be correct. The illustrative example will evaluationsamples in which the evaluation sample itself is mislabeled.

Although some embodiments of the invention use the same recognitionsystem with either of the linked models active for labeling the practicedata, for the illustrative example assume that, either a differentrecognition system is used or that the active models are the ones inwhich the particular training sample is skipped.

The evaluation samples that will contribute to the evidence ofcomparative performance will be samples in which the word “frog” or oneof its phoneme models actually occurs as part of the best scoring answeror an answer with a score close to the score of the best scoring answer.

In the case of the phoneme /r/, this will include instances of wordsthat actually contain /r/ and a random selection of other words that aremisrecognized as words that contain the phoneme /r/. For the model ofthe phoneme /r/ in the context of a preceding /f/ and a following /aw/,the evaluation samples will come from samples in which any of a limitedset of words such as frog, fraught, froth, etc. is either the top choiceor a close score.

The models for the phoneme /r/ that skip the particular sample will benormal acoustic models for /r/. The models for the phoneme /r/ trainedon the particular sample (which doesn't actually contain an /r/) willhave performance results that are somewhat degraded.

Of the evaluation samples in which /r/ occurs as a top choice or closecall, some of these evaluation samples will actually have an instance of/r/ and some of them will not have an instance of /r/. For theevaluation samples that do not include an actual instance of /r/ thedirection in which the acoustic model for /r/ is degraded is randomrelative to the direction of the difference between the nominal labelfor the practice sample and the best close scoring other word. That is,in such cases the change in the /r/ model is equally likely to improvethe recognition performance or to make it worse. This conclusion is trueregardless of the error rate in the labeling of the practice data.

In practice, the error rate in labeling the practice data can bemeasured and the criteria for selecting the evaluation data can be tunedto optimize the efficiency at accumulating data for rejecting the nullhypothesis. For purpose of the illustrative example, assume thefollowing criterion for the selection of evaluation data. This selectioncriterion has been chosen not for efficiency but rather to simplify thetheoretical analysis for the illustrative example. For evaluation datafor the null hypothesis for the linked models for the phoneme /r/,select only data in which either the top choice answer or a very closescoring second best answer contains an instance of the phoneme /r/.Also, only select samples in which one of the two top scoring hypothesescontains and /r/ and the other one doesn't. If a recognizer choserandomly between these two close choices, then it would be correct halfthe time.

Consider now the practice samples that actually contain an instance of/r/. Any recognition system that does better than chance will rank thehypothesis that contains an /r/ as the top choice more than half thetime. Since the practice samples now being considered all contain anactual /r/ and the /r/ model is degraded, the relative score of thehypothesis containing an /r/ will usually be made worse by the degradedmodel. More than half the time this model will be the top scoring model,so most of the time the worse score of the hypothesis that contains the/r/ will be judged as making the score worse for the correct answerrather than for an incorrect close call.

Thus, for data that does not contain an /r/ there is on average noaccumulation of evidence in favor of either model, for data that doescontain an /r/ with practice data labeled any better than by chancethere will be a bias toward rejecting the null hypothesis in favor ofthe conclusion that training on the particular sample makes theperformance worse. Thus, the chance of rejecting the null hypothesis infavor of the conclusion that training on the particular sample makes theperformance better is less than the specified statistical significancelevel, say less than a probability of 0.01, and otherwise the processwill eventually reject the null hypothesis in favor of the conclusionthat training on the particular sample makes the performance worse.

A similar analysis applies to the word model for the whole word “frog”and to the context-dependent model for the phoneme /r/, except thatinstances of these hypotheses will be much less frequent so it will takemuch longer to accumulate statistically significant evidence that thenull hypothesis is false.

On the other hand, the one-shot models created by the process shown inFIG. 4 may be able to reject the null hypothesis much more quickly.Although FIG. 4 has not yet been discussed in detail, all we need toknow for the purpose of this example is that a new model is createdbased just on the single instance that is available from the particulartraining sample. In the example, the training sample is actually aninstance of the word “fog” and the new model for the phoneme /r/ willprobably be taken from the initial portion of the phoneme /aw/. Becauseit is actually a sample of an /aw/, this new model will match very wellagainst most instances of the phoneme /aw/ and will almost never matchwell against any instance of the phoneme /r/. For purpose of theexample, assume that the recognition system used to label the practicedata is robust against some of its models being poor. For example,assume it has multiple models for each sound or has multiple lower-levelclassifiers. Then, the new model for the phoneme /r/ will usually onlyactively participate in the recognition decision when the actual speechsample contains an /aw/. However, it also obviously can only participatewhen one of the hypotheses contains an /r/. Thus, the evaluation sampleswill primarily consist of instances in which the hypotheses contain both/r/ and /aw/. The new model for /r/ will systematically improve thescore for word hypotheses that contain an /r/ followed by an /aw/whenever the actual speech contains only an /aw/. Furthermore it willsystematically degrade the score for any word hypothesis that containsan /r/ whenever there actually is an /r/. That is, it willsystematically improve the scores of the incorrect answers orsystematically degrade the scores of the correct answer, depending onwhether an actual /r/ is present. In either case it degrades therelative score of the correct hypothesis compared to the incorrecthypothesis. In other words, evidence will rapidly be accumulated toreject the null hypothesis in favor the conclusion that creating a newmodel from the particular training sample degrades performance at astatistically significant level.

As a second illustrative example, refer to the OCR example discussedfollowing FIG. 3. In that example, the smudged character is correctlylabeled in the training data, but of course is smudged. Therefore,further assume that the particular smudged training sample is flagged asan outlier by block 303 of FIG. 3. Then the process of FIG. 4 is appliedwith respect to the particular training sample. In particular, a newmodel is created by block 411. Because the additional model requiresadditional resources, the null hypothesis test is slightly differentthan for the embodiment shown in FIG. 3. The test is one-sided andasymmetric. The version of the module with the new model must performbetter by an amount that is not only sufficient to reject the nullhypothesis at a statistically significant level, but must also improveperformance by an amount that makes up for the additional resourcesrequired to implement the additional model. Furthermore, the linkedallele associated with the Socratic agent created in block 402 has asomewhat different form. In this case, the linked pair comprises a oneversion of the classifier module in which the extra model is present anda second version in which the extra model is not present.

Continuing with the example, suppose that there are a large number ofsmudged characters. Eventually a large number of new models will becreated. One embodiment addresses the potential problem of an excess ofmodels. Block 421 obtains an existing model or module to be tested bythe process shown in FIG. 4. This model or module does not need to be amodule or module that was originally created by one-shot learning as inblock 411. It can be any model or module. In the illustrative example,assume that an excess of smudged models eventually accumulates. In oneembodiment, the performance metric for the comparative performancemeasurement in block 406 is the performance of the overall system withall of the models currently active, in particular all of the modelscreated from smudged training samples. Then, if there is an excess ofsmudged models, measurements performed for some of these smudged models,will no longer be adequate to pass the asymmetric test set up by theSocratic agent. Therefore, eventually the process will come to block 410and the model being tested will be deleted.

Thus, in the example it can be seen that models and modules can both beadded and deleted. The same testing process may also be applied toelements within a data structure, such as nodes and arcs within a graph.Thus, the process of FIG. 4 can be applied to a kind of learning otherthan just estimating the parameters in a given set of models. By addingand deleting models and adding and deleting elements within a datastructure, the process of FIG. 4 also learns new structure. One dangerin attempting to learn new structure is that any structural change islikely to make some things better and some things worse. Therefore it isdifficult to decide whether a particular change will make an overallimprovement in performance based on a single example or a small numberof examples. In particular, it is hazardous to try to estimate theperformance impact of a structural change based on the data that causedthe structural change to be hypothesized. One embodiment of theinvention, as illustrated in FIG. 4, avoids most of this hazard. Thedecision to accept a structural change is based on independentstatistical evidence gathered from a significant number of samples andthe evidence must be sufficient to reject an asymmetric, one-sided nullhypothesis at a statistically significant level. Furthermore, even if astructural change is incorrectly accepted or if the situation changes,there is a mechanism (selecting the given change to be tested, startingin block 421) for detecting that the change is no longer successful andfor reversing it.

In summary, the process shown in FIG. 4 involves essentially the samesteps as the process shown in FIG. 3, with just a few key differences.One difference is that the process in FIG. 3 measures comparativeperformance of an allele of linked models in which the linked modelseach have the same number of elements and use essentially the samecomputational resources. The linked models in FIG. 4, on the other hand,have differing numbers of elements and use differing amounts of computerresources. This difference then results in other differences. Forexample, the null hypothesis test in FIG. 4 is one-sided and is offsetor biased to compensate for the cost of the additional computationalresources.

FIG. 5 is a flowchart of the process by which one embodiment of theinvention gathers information about a given knowledge item or designchoice. Block 510 chooses a particular knowledge item or design choiceto monitor. A knowledge item may be any discrete piece of knowledge inthe classifier module. For example, it could be a single training sampletogether with the associated putative label. As a second example, itcould an optional context-dependent model transformation rule. A designchoice could be any decision point in the design of a patternrecognition system, such as the analysis bandwidth in the signalprocessing. In a typical classifier module or pattern classificationsystem, there will be a large number of knowledge items and a largenumber of design choices in the system design process. Thus, there are alarge number of possible selections for block 510. In one embodiment,the process of FIG. 5 can be done many times with different selectionsin block 510, which will lead to the creation in block 530 of manydifferent, semi-autonomous Socratic agents. Furthermore, even for asingle knowledge item in a complex system the knowledge item might be ahierarchy or other data structure involving a number of knowledge itemsrelated to subunits of the first knowledge item. Therefore, even for asingle knowledge item there may be more than one Socratic agent.

For any selected knowledge item, there is also an implicit designchoice. For example, for a given training sample, either the trainingcan be included in the model training, or the sample could be rejectedand be excluding from the model training, as in the example mentioned inthe discussion of FIG. 3. As another example, a given context-dependenttransformation rule may either be applied or may be ignored. From anyexplicit design choice or implicit design choice in the trainingprocess, two sets of models may be created by following each alternativein the design choice. Block 520 creates two such sets of models andbuilds cross-reference data structure such that whenever one of thepaired sets of models is used in the recognition process, therecognition results can be recomputed using the alternative model setand both sets of recognition results can be obtained and compared. In atypical embodiment, the difference in the two model sets may belocalized to a small portion of the overall model set. There then may bemany such small changes being monitored at different sites within themodel set. The paired-model sets with such a localized change may becalled a paired-model allele.

Notice that the Socratic agent for delayed-decision training shown inFIGS. 3 and 4 is a special case of a paired-model allele in which onemember of the pair has models obtained from training on the designatedtraining sample and the other member of the pair has models obtained bynot training on the designated training sample. In the more general caseshown in FIG. 5, one member of the paired-model allele results from onedecision alternative in block 510 and the other member of the alleleresults from another decision alternative in block 510. In fact, inspite of the name paired-model, a paired-model allele is not limited toonly two members. If the design choice selected in block 510 has morethan two alternative decision possibilities, then the allele will havemore than two sets of models that are associated through the allele.Hence, the more general name is a linked-model allele. When there aremore than two members in the allele, the null hypothesis is that all thedecision alternatives have equivalent performance, and the sequentialdecision test is terminated as soon as enough evidence is accumulated toreject the null hypothesis in favor of any one of the allele members.

Block 530 creates a Socratic agent associated with the linked-modelallele for the knowledge item or design choice selected in block 510.Block 540 collects statistics comparing the relative performance of thelinked sets of models for a plurality of evaluation data samples. In oneembodiment, the Socratic agent formulates a null hypothesis, that is,the hypothesis that there is no difference in performance of the linkedsets. Then, block 540 collects comparative performance until enoughevidence has been accumulated to reject the null hypothesis in favor ofone of the alternative model sets. The testing may be continued untileither the null hypothesis is rejected at a specified level ofsignificance or until a specified criterion is met, such as anindication that cost of further testing exceeds its expected value.

After comparative performance data has been collected until a specifiedstopping criterion has been met, block 550 feeds back the accumulatedinformation to a knowledge representation associated with the knowledgeitem selected in block 510.

Block 560 tests whether there are additional Socratic agents that mightaccumulate evidence for a given knowledge item. If so, control returnsto block 540 to continue testing with another Socratic agent related tothe given knowledge item.

The process then proceeds to block 570, where it is determined whetherthe process is completed. If not, the process continues by selectinganother knowledge item or decision point to be tested.

The processes shown in FIGS. 3, 4 and 5 have quite a bit in common. Thecommon elements comprise the following steps:

-   -   1) Create a Socratic agent associated with a given lower-level        classifier module, with an allele linking two or more models        such that any one of the models may be made the active model in        the given lower-level classifier module.    -   2) In the Socratic agent create a null among the set of two or        more models.    -   3) Accumulate evidence to accept or reject the null hypothesis.        Continue collecting evidence until either the null hypothesis is        rejected at a statistically significant level or until a        stopping criterion is met.    -   4) Transmitting the accumulated evidence or a summary of the        accumulated evidence back to the data structure or software        associated with the origin of the models. In FIG. 3, the        original of the models is the particular training sample. In        FIG. 4 it may be a training sample plus the associated creation        of a new model by one-shot learning. It may be a model modified        by a change in structure. It may be an existing model that is        being tested to see if its incremental contribution is worth its        cost. In FIG. 5 it is a decision point in which different models        result from different decisions.

In any of the cases, if the null hypothesis is rejected, the bestperforming model in the allele is made the one active model in therecognition process.

FIG. 6 is a flowchart of a particular application of the process shownin FIG. 5.

FIG. 6 shows the application of the performance feedback to correcterrors in the labeling of training data.

Block 610 obtains a collection of training data with labels. Innon-Socratic model training it is important to have a very low errorrate in the labels associated with the training data. Because theprocess illustrated in FIG. 6 can correct errors in the training data,it is more tolerant of errors in the labeling of the training data thanis non-Socratic training. Therefore, block 610 may obtain the labels forthe training data by a less expensive process than would be needed toobtain a set of labels with a very low error rate. In particular, block610 may obtain labels for the training data automatically by running arecognition process, rather than requiring the labels to be marked byhuman labor.

Block 620 selects a particular set of training samples to have theirlabels tested.

Block 630 creates a Socratic agent for each label under test.

For each label under test and its associated Socratic agent, block 640performs the delayed-decision testing illustrated in FIG. 3 on aplurality of evaluation data samples. The training done by block 640 maybe discarded, because the purpose in the context of FIG. 6 is to correctthe training labels not to do the training. However, the feedbackinformation is retained and added as an annotation to the particulartraining sample label. The feedback information includes the results ofthe testing of the null hypothesis, in particular whether the nullhypothesis has been rejected either indicating improved performance ordegraded performance from training on the given training sample with itsassociated label. In one embodiment, the annotation information isstored for use in subsequent analysis. In particular, in a complexrecognition system the given training sample may actual represent acomplex data structure with associated labels. In speech recognition,for example, if a word label is incorrect, then usually one or more ofthe associated phoneme labels will also be wrong. In addition, trainingsamples that are actually mislabeled are likely to be determined to beoutliers by block 303 of FIG. 3, so that a tentative new model will becreated and tested by the process of FIG. 4 as well as the allelecreated and tested by the process of FIG. 3. The annotations then wouldstore the information from one of these processes to be combined withthe feedback information from the other process. In making a decision asto whether a label is wrong or whether a particular training sample issimply very noisy, in one embodiment null hypothesis testing feedbackinformation will be stored and accumulated across multiple unit typesassociated with a given training sample before a consensus decision isattempted.

If there is feedback from more than one Socratic agent, then block 650determines whether there is a consensus. In one embodiment, theconsensus rules will depend on the amount of data available and on adesign criterion as to whether or not to be conservative in acceptingquestionable training data. With lots of data and a conservative designcriterion, a training sample may be skipped if even one Socratic agentreports back that using the training sample decreases performance. Sincesome Socratic agents may accumulate less evidence, for example if theyare monitoring a rare type of event, then some Socratic agents that mayreject the null hypothesis while others fail to reject the nullhypothesis before reaching some stopping criterion. In such a case, inone embodiment it would be regarded as a consensus as long as all theagents rejecting the null hypothesis are in agreement as to thedirection of the reject. That is, as long as all either agree thatperformance is improved or if all agree that performance is worse for agiven alternative.

Block 660 corrects the marked training sample labels. That is, for anytraining sample label which decreases the performance of the system, thetraining sample is marked to be skipped in future training, or the labelis changed to a label for which the training sample with the changedlabel improves performance. The entire set of training data, with therejected samples of corrected labels may be used to run training tocreate a new set of models. They also may be used to train otherclassifier modules.

FIG. 7 is a flowchart of a process in a particular embodiment of theinvention in which the labels both in the training data and in thepractice data are corrected.

Block 710 labels a set of training data. In the embodiment illustratedin FIG. 7, block 710 automatically labels a set of training data usingall available knowledge. That is, block 710 uses any other classifiermodules that may be available in addition to the classifier module beingtrained. In speech recognition, handwriting recognition or opticalcharacter recognition, block 710 may use knowledge about theprobabilities of word sequences, such as a statistical language model,in addition to the models of the sounds or text characters in theclassifier module being trained.

Block 710 also uses any prior knowledge or partial labeling of thetraining data. For example, it may use close captioning of the audiofrom television broadcasts or subtitles for movies or videos, eventhough closed captioning or subtitles are often far from being accurateverbatim transcripts. However, if no prior information or otherclassifier modules are available, block 710 simply runs automaticrecognition with the best models currently available.

Block 720 automatically labels the collection of practice data. Thispractice data is to be used for delayed decision training, asillustrated FIG. 3 and FIG. 4. Block 720 also uses all availableknowledge. However, for the illustrated embodiment of block 720 theautomatic labeling in block 720 should use at least one source ofknowledge other than the classifier module being trained.

Block 730 then performs delayed decision training as illustrated in FIG.3 or FIG. 4 to obtain feedback information as illustrated in FIG. 6.Block 730 uses the feedback information to correct the labels in thetraining data.

Block 740, which is optional, interchanges the roles of the training setand the practice set, and uses the process of blocks 710 through 730 tocorrect the labels in the data that at first was used as practice data.Thus, the labels in both the original training data and in the originalpractice data are corrected. With the corrected labels, the trainingdata may then be used either for non-Socratic training or for anadditional round of delayed decision training. For non-Socratictraining, the original practice data may be combined with the originaltraining set to create a larger training set.

Block 750 checks whether the process should be repeated with the nowimproved labels.

FIG. 8 is a block diagram of an embodiment of the invention with aspecialized Socratic agent with knowledge about the knowledge of aplurality of related lower-level classifier modules. In this embodiment,the Socratic agent not only has knowledge about the collection ofrelated lower-level classifier modules, but actively controls the use ofthe lower-level classifier modules during recognition and controls theirtraining process. Such an active multi-classifier module Socratic agentis called a Socratic controller.

In reference to FIG. 8, in this embodiment there are a plurality ofrelated lower-level classifier modules 810 that are controlled by asingle Socratic controller 830. In relation to this embodiment, each ofthe related classifier modules is a pattern classifier such that all ofthe related classifier modules share the same set of target classes. Theindependent classifier modules 820 are other classifier modules thatwork cooperatively with the related classifier modules 810 on an overalltask, but the independent classifier modules 820 do not necessarily havethe same target classes as the related classifier modules 810.

The Socratic controller 830 will be discussed in more detail inreference to other Figures. It represents and acquires knowledge aboutthe knowledge of the collection of related classifier modules 810. Forexample, in one embodiment it models, as a function of the data and thecontext, the knowledge of each individual classifier module 810 relativeto the knowledge of the other related classifier modules 810. In atypical embodiment, each of the lower-level classifier modules will haveas input a vector of values for a number of observations or measurementscalled “features.” For example, in image recognition the features mayinclude the raw values of the color and intensity of individual pixelsin the image. The input data features may also include measurements orderived features, such as rate of change or the gradient of theintensity, or even more complex features such as whether or not an edgehas been detected at a given location. With the plurality of relatedlower level classifier modules, different input features may be used bydifferent modules in the collection of modules. In a typical embodimentof one lower level classifier module, the module computes as output thevalue of the class that the particular lower level classifier modulebelieves best matches the given input features. In another typicalembodiment, the lower level classifier module computes as output a scorefor each candidate class, indicating how well the particular lower levelclassifier module believes the particular candidate class matches thegiven input features. In addition to the union of all the featureobservations that are available to the individual lower level classifiermodules 810, the Socratic controller 830 also observes the outputclassification results and associated scores computed by the relatedlower level classifier modules 810.

Given these observations, in one embodiment the Socratic controller 830itself has a pattern recognition task. However, this is a higher-levelindirect pattern recognition task, not directly the task of recognizingthe correct class in the set of target classes. Rather, the Socraticcontroller represents and acquires context-dependent knowledge about theperformance of the lower-level related classifier modules 810. That is,it performs a pattern recognition task in which the output is notdirectly a class label among the target classes, but rather a vectorwith a component for each of individual lower-level related classifiermodules 810. The component corresponding to a particular lower-levelclassifier module 810 is the estimate by the Socratic controller 830 ofthe likelihood that the particular related lower level classifier module810 is correct in the current classification. These estimatedlikelihoods are then used by Socratic controller 830 in the process ofcombining the results from the individual related classifier into asingle joint classification. This process is explained in more detail inother Figures.

In relation to the FIG. 8, it is important to understand that theSocratic controller 830 performs a classification task, but that thispattern classification task is based on higher-level knowledge aboutknowledge, and this classification task takes a very different form thanthe direct classifications performed by the lower-level relatedclassifier modules 810. For example, as a function of the data observedby the Socratic controller 830 in a given instance it may be determinedbased on training on similar data that a particular one of the relatedlower level classifier modules 810 is very reliable in a region of thespace of possible data feature vectors that includes the currentinstance. In this region of the data space there may be subregions inwhich different classes from the set of target classes are more likelyto be the correct class. Each of the lower-level related classifiermodules will attempt to correctly classify the target class in each ofthese subregions.

Thus the data space partitioning task for the Socratic controller 830 isvery different from the pattern recognition task of one of thelower-level classifier modules. Each lower-level classifier module isattempting to match the correct class label. To the extent that thepattern recognition task of one of the lower-level classifier modules isviewed as a data space partition task, the lower-level classifier moduleis attempting to partition the space to separate regions in whichdifferent classes are the correct label. The Socratic controller 830,however, only attempts to separate regions in which there is a change asto which lower-level classifier modules are likely to be reliable. Thatis, the Socratic controller 830 does not attempt to separate two regionsof data space in which different classes are the correct label, so longas the same lower-level classifiers are expected to be correct in theirlabeling (even though the actual labeling will change in agreement withthe correct class label).

Thus, it can be seen that even though the Socratic pattern recognitionproblem is a standard pattern recognition problem, it has a verydifferent form than the lower-level pattern recognition problem. Thereare many possible embodiments for implementing the Socratic patternrecognition done by the Socratic controller 830 in estimating thereliability of the lower-level related classifier modules, because oncethe pattern recognition task of the Socratic controller 830 isrepresented as a separate pattern recognition problem, any one of manystandard pattern recognition techniques may be used. Later Figures willexplain in more detail specific aspects of how the Socratic controller830 may be implemented in one embodiment.

Referring again to FIG. 8, in one embodiment there may be a large numberof related classifier modules 810 controlled by a particular Socraticcontroller 830 and a large number of independent classifier modules. Forefficiency, it may be desirable to have only a fraction of all therelated classifier modules controlled by the Socratic controller 830active. Therefore, block 840 selects a subset of the related classifiermodules to be active in each particular instance. In one embodiment, theSocratic controller 830 performs this selection process for itsassociated related classifier modules 810. It performs this selectionbased in part on the estimate of reliability that has been discussedabove. For example, in one embodiment the active subset may be selectedas described in relation to FIG. 10.

Block 850 combines the results of all the active classifier modules. TheSocratic controller 830 combines the results of the active relatedclassifier modules 810 based in part on the estimated reliability. Forexample, the Socratic controller 830 may determine a set of weights forweighted voting by fitting the observed reliability data as a regressionproblem as described in relation to FIG. 10.

Using all of the available knowledge, block 860 uses the best availablerecognition system to label practice data to be used fordelayed-decision training of individual classifier modules 810, asexplained in FIGS. 3 and 4, and for training the Socratic controller830.

Block 870 measures the performance of the related classifier modules 810on the practice data. These performance measurements are used fortraining the pattern recognition task performed by the Socraticcontroller 830 in estimating the reliability of each of the relatedclassifier modules 810 in a particular instance.

A Socratic agent is any higher-level classifier module that containsknowledge about the knowledge of at least one other classifier module.The mechanism of creating alleles of linked models and of testing nullhypotheses about these linked models has been discussed with referenceto FIGS. 3 and 4. A Socratic controller is a Socratic agent that has aplurality of associated lower-level modules. Moreover, several newmechanisms for acquiring, evaluating and utilizing knowledge about thisplurality of associated lower-level modules are introduced inembodiments of Socratic controllers associated with certain aspects ofthe invention. In particular, in one embodiment, a Socratic controllerwill perform one or more of the following processes:

1) it will measure the performance of the plurality of associatedlower-level classifier modules as a function of the data available tothe Socratic controller for each sample to be recognized and will solvea higher-level pattern recognition problem to determine parameters forcombining the results of the lower-level modules such that the combinedresult is dependent on the data available to the Socratic controller forthe given sample being recognized;

2) it will solve a pattern recognition problem that, as a function ofthe data available to the Socratic controller, estimates which subset ofthe plurality lower-level classifier modules is likely to be mostreliable for classifying a particular data sample;

3) it will actively select a subset to the lower-level classifiermodules based on the estimate of their reliability for a particular datasample;

4) it will actively control the training of the plurality of lower-levelclassifier modules to optimize their joint performance.

A Socratic controller is not just another classifier module. It differsin several ways. First, the Socratic controller has data that is notavailable to the individual lower-level classifier modules. To beginwith, it has the total of all the data available to all of thelower-level classifier modules, whether or not that total data isavailable to any individual lower-level classifier. More significantly,the Socratic controller has available as input data the output resultsof the plurality of lower-level modules. A lower-level classifier modulemay always observe its own output results. It also may receive as inputdata the output of a yet lower-level module. However, under theprinciple of modularity, if two or more of the lower-level “modules”both receive output results from each other, they would no longer beconsidered distinct modules but rather would be regarded as beingcombined into a single composite module. Such an architecture ispossible even for the entire plurality of lower-level modules associatedwith a Socratic controller. If any of the functions of a Socraticcontroller are implemented in such an inter-communicating compositemodule system, it should be regarded as an alternate, less modular,embodiment of a Socratic controller.

In reference to an example of a modular embodiment, the Socraticcontroller thus has input data not available to the lower-level modules.The greatest distinguishing characteristic, is that the Socraticcontroller solves a very different pattern recognition problem than anyof the lower-level classifier modules. Each lower-level classifiermodule tries to recognize the correct class label for each data sample.The Socratic controller, however, does not try to directly recognize theclass of the data sample. Instead, it tries to recognize which of thelower-level classifier modules is most likely to correctly identify agiven data sample.

At first glance it might appear that the Socratic controller has a muchmore difficult pattern recognition problem than the lower-levelclassifiers. Can a Socratic controller solve this problem well enough toimprove the overall system performance? Might it actually make theoverall performance worse?

Just as informative example, consider an embodiment of a Socraticcontroller that uses only a small part of its available information.This simplified example will show that even a restricted Socraticcontroller can do at least as well as system without a Socraticcontroller. For this example, assume that the recognition system is anoptical character recognition system, that the particular lower-levelclassifiers being discussed classify characters based on their opticalimages, and that the overall recognition system also has availableknowledge of the vocabulary and of the likelihood of particular wordsequences. A similar example would be a speech recognition system inwhich the lower-level classifiers for the example Socratic controllerare phoneme recognizers.

Just for this informative example, assume that the Socratic controllerrestricts the input information that it uses: assume it takes the outputresults of the best performing individual lower-level classifier, butignores all other input data available to the Socratic controller. Inspecifying the higher-level pattern recognition problem for the exampleSocratic controller, use the particular lower-level classifier as areference. As output to the higher-level classification problem,estimate results from each lower-level classifier sample on data ascorrect if it agrees with the chosen reference lower-level classifierand as incorrect if it disagrees with the chosen reference.

By construction, this example Socratic controller will solve thehigher-level classification problem such that the end result is no worse(and no better) than the best performing individual lower-levelclassifier. This example demonstrates that it is straight forward todesign a Socratic controller that at least doesn't make things anyworse.

Furthermore, this simple example Socratic controller can be easilymodified to one that will at least incrementally improve itsperformance. Note that the lower-level classifier was used as areference only for the purpose of specifying a particular embodiment ofa higher-level pattern recognition problem for the example Socraticcontroller. For practice data, other information is available forestimating the correct answer for each practice sample, for example thefinal output of the overall recognition system including knowledge ofthe vocabulary and word sequences, not just the character recognition inisolation. Assume for the example that there is at least one datacondition that can be detected under which there is some otherindividual lower-level classifier that performs better on practice datathan the chosen reference classifier module. For example, suppose thatwhen two particular other lower-level classifier modules happen toagree, then the answer that they agree on performs better than theanswer of the reference module. By running an on-going process ofcontinuing to search for such conditions, a Socratic controller couldmake an indefinite number of incremental improvements by looking atadditional data features as input and training on practice data, nolonger just taking the single best individual lower-level classifier asa reference.

From this example, it is clear that a system with a Socratic controllercan do at least as well as a corresponding system with the samelower-level classifier modules without a Socratic controller, in spiteof the apparent complexity of the higher-level classification problem.Furthermore, it is apparent that further improvement can be achievedmaking the final classification result depend on tests on the dataavailable to the Socratic controller. That is, the higher-levelclassification process can further improve the overall performance.Embodiments of these processes will be described in more detail inreference to the following diagrams.

FIG. 9 is a flowchart of a process by which a Socratic module, such asthe Socratic controller 830 in FIG. 8, may be trained in the Socraticpattern recognition problem of estimating the reliability of thelower-level classifier modules.

Block 910 obtains a set of practice data. Then block 920 controls a loopsuch that blocks 930 through 970 are performed for each item in thepractice data. It is to be understood that, in some embodiments theprocess of progressing from item to item in the practice data may bemore complex than simply indexing though a sequence of items. Forexample, in continuous speech recognition, the system may performrecognition of complete sentences as units. However, the lower-levelcomponent classifier modules for the particular higher-level classifiermodule being trained would typically model shorter units, such as wordsor phonemes. In such a case, the control block 920 would actually beimplemented as a multi-level control block that would index throughsentences, performing a system-level recognition task for each sentence,and then would index through the shorter units within each sentence.

Block 930 obtains classification results from each of the componentlower-level classifier modules. In the embodiment illustrated in FIG. 8,these component lower-level classifier modules are the relatedclassifier module 810. In one embodiment, if there are a large number ofcomponent classifier modules, there may be a selection of a smalleractive subset, in which case block 930 obtains results only from theactive subset.

Block 940 assembles the results from component classifier modules into apattern form. The particular pattern form may be chosen by the designerto fit a particular application. In one illustrative embodiment, avector is formed with one bit for each component classifier module. Thebit for a particular component classifier module would be a 1 if theparticular component classifier module makes a correct classificationfor the given item and is a 0 if the particular component classifiermodule makes an incorrect classification. In another embodiment, inaddition to the bit vector just described, there would also be a vectorformed, with a numerical score computed by each component classifiermodule.

Block 950 uses the pattern form created in block 940 to create atraining sample for the pattern recognition task being performed by theSocratic controller. In this training sample the input observationswould include the union of all the input observations of all thecomponent classifier modules. The input observations would also includeany output results obtained from the component classifier modules. Inaddition to the particular best label chosen by each componentclassifier module in its pattern classification task, these outputresults may include other things computed by the component classifiermodule, such as the score of the best scoring class, a vector ofestimated a posteriori probabilities for all the target classes, or ascore indicating the component classifier module's own estimate of itslikelihood of being correct in this particular instance. The targetoutput for the Socratic controller for this particular set of inputobservations would be the pattern form assembled in block 930. Thus,together these input observations and this target output would form astandard input-output pair of a training sample. That is, these inputobservations are given as a training sample with the target outputdesignated as the correct “answer,” and one sample of trainingstatistics is accumulated by the designated training process.

Block 960 accumulates training statistics from multiple training samplesas the loop from 920 to 970 is executed multiple times.

Block 970 checks to see if a stopping criterion is met. The stoppingcriterion may simply be that there is no more practice data available.If the stopping criterion is not met, control returns to block 920 toget another practice item.

If the stopping criterion is met, control proceeds to block 980, whichupdates the models in the Socratic controller.

FIG. 10 is a flowchart of the operation of a multi-module controllersuch as a Socratic controller. FIG. 10 illustrates the operation in arecognition task, rather than in the training process.

Block 1001 obtains a data item to be recognized.

In one embodiment, the Socratic controller, or other multi-modulecontroller, may have many component modules, so there are two points inthe process at which a smaller subset of the modules may be selected asthe active subset. Block 1002 checks to see whether such a selection ofan active subset should be performed based on the directly observed dataalone.

If such a selection is to be performed, control passes to block 1003,which performs such a selection. In one embodiment, the selection wouldbe based in part on the estimated reliability of the componentlower-level classifier modules, as estimated by the higher-level,multi-classifier module controller or Socratic controller. If aselection of an active subset is performed by block 1003, then theinactive component classifier modules do not need to perform anyclassification for the obtained data item, so a considerable amount ofcomputation may be saved.

If block 1002 determines that no active subset selection is to beperformed at this stage, then all the component classifier modules areactive and control passes directly to block 1004.

Block 1004 obtains results from all of the active component classifiermodules for the data item.

Block 1005 checks whether the selection of a smaller active subset is tobe performed at this stage. At this stage, the selection process hasavailable the component output results obtained in block 1004 as well asthe original obtained data item. Therefore, in some embodiments it isbeneficial to perform a further, more precise selection.

If a subset selection is to be performed at this stage, block 1006performs that selection. The selection is based in part on thehigher-level module's estimate of the reliability of the lower-levelcomponent classifier modules for the particular obtained data item.However, at this stage the input data for this Socratic patternclassification problem includes the comparative results of all of theactive lower-level classifier modules and the scores and confidencemeasures computed by these active components.

In some embodiments, there may be a large number of component classifiermodules, including classifier modules that specialize in handlingparticular situations. In this case, the number of active componentsselected at this stage may be a very small, sparse subset of the totalset of component classifier modules. Restricting the active componentsto such a small subset greatly simplifies the problem of training theweights or other parameters used in the process of combining thecomponent results into a single overall result.

Blocks 1007 through 1009 illustrate one particular embodiment for theprocess of combining the component results. However, any general methodof non-linear regression may be used for this process.

Block 1007 generates a specified set of non-linear functions. In oneembodiment, the component modules are trained to work cooperatively,rather than merely being trained independently on each component'sindividual task. The training process may include collecting statisticson correlations among the results of the component modules. In someembodiments, new specialized components may even be created specificallyto handle cases in which the previous components fail. Thus, there isknowledge about the correlations and interactions among the componentmodules. In one embodiment, the non-linear functions generated by block1007 will include functions of products of scores and bilinear and otherfunctions with variables from more than one component.

In the illustrated embodiment, block 1008 computes a weighted regressionfunction in the expanded vector space that includes the values of thenon-linear functions computed in block 1007, as well as the featurevalues of original obtained data item and the output results of theactive component classifier modules.

Finally, block 1009 returns the computed composite score and/orclassification result.

FIG. 11 is a flow chart of a process that may be used in someembodiments as part of the process of a Socratic controller estimatingthe reliability of a collection of lower-level component classifiermodules. The process shown in FIG. 11 is more general, however, and maybe applied as a method of training a pattern recognition system in anysituation in which it is expected that different models should be usedin different parts of the data space.

Block 1110 obtains a partition of the data space. For example, thisinitial partition may be obtained by building a decision tree to solve aspecified classification problem with each element or sector in the dataspace representing a region of data for which the classificationdecision is a particular value.

Block 1120 chooses an element of the partition obtained in block 1110.That is, it chooses one of the regions into which the data space hasbeen divided.

The underlying concept is that a different set of models may be trainedin each element of the partition. The process shown in FIG. 11, however,is focused on a particular sub-problem. The process shown in FIG. 11uses the technology of Socratic agents to optimize the assignment oftraining samples to elements of the partition.

Block 1130 trains a classifier module to recognize patterns for aspecific classification task, but restricted to data items from thechosen element of the partition. Different models and even differentclassifier modules may be used in different elements of the partition.In particular, in some embodiments the partition may be used in theprocess of selection of active components in a multiple componentSocratic controllers such as shown in FIGS. 8 to 10.

Block 1140 selects a sample from the chosen element of the partition.This sample is chosen as a candidate for transfer to a differentpartition element. Preferably, the sample will be selected based onmeasurements that indicate that the classification of the selectedsample will be better using the models and classifier modules in the newelement than in the current element. However, the overall process shownin FIG. 11 does performance optimization, so even a random selection ofa sample in block 1140 will work, but perhaps less efficiently.

In one embodiment, typically the partition will be determined by afinite set of training samples, with the partition being computed basedon these training samples. Preferably, block 1140 chooses one of thesetraining samples or adds the chosen sample to the training set. Thechosen sample is not explicitly transferred to a different element ofthe partition, but the partition is merely recomputed with the chosensample labeled in training so as to be attempted to be assigned to thenew partition element. This process is called a soft transfer ratherthan a hard transfer. When a transfer is completed, it signifies thatthe sample that has been transferred is more consistent when groupedwith region to which it has been transferred, in that the performance isimproved when using the new partition compared to using the partitioncomputed from the sample assignments from before the transfer.

Block 1150 tests whether the performance, comparing the performancedoing the selected soft transfer versus not doing the selected softtransfer. In one embodiment this comparison is done as adelayed-decision test by a Socratic agent. The Socratic agent creates apaired-model structure and performs a sequential decision test of thenull hypothesis. The null hypothesis in this case is that theperformance is the same whether or not the soft transfer is done.

Block 1160 tests whether or not the null hypothesis for a particularSocratic agent can be rejected at the specified level of statisticalsignificance. If so, the accumulation of evidence for a particularSocratic agent may be terminated. If not, control is returned to block1150 and further evidence is accumulated for the particular Socraticagent.

In one embodiment, many such Socratic agents may actively be evaluatingtheir null hypotheses at the same time. One implementation would be amulti-threaded process with each Socratic agent running in a distinctthread. In FIG. 11, this process is represented by the fact that in thetest in block 1160 even if the current Socratic agent is not finishedthe process creates a thread that proceeds to block 1170, in addition tothe returning to block 1150 to continue with the current Socratic agent.

Block 1170 tests whether the process should merely continue with theselection of another sample from the current partition or if controlshould instead return to block 1120. Control should return to block 1120if either a stopping criterion is met that indicates that the currentpartition element has been processed enough, or if a stopping criterionis met that indicates that the number of changes made in the partitionis such that the block 1130 training of the models specific to a givenpartition element should be recomputed.

If neither stopping criterion is met, control returns to block 1140 anda new sample is selected as a candidate to soft transfer to a differentpartition element. If either stopping criterion is met, control goes toblock 1120 to again choose a partition element. The choice in block 1120is with replacement. That is, a previously chosen partition element maybe chosen again. In the one embodiment, the process continuesindefinitely, so each partition element is chosen many times as thesystem continues to evolve. However, if for any reason, it is desired tohave a stable partition, the process of FIG. 11 may be suspended for anarbitrary period of time and the partition elements may be frozen assoon as all the active Socratic agents terminate.

FIG. 12 is a flowchart of one embodiment for the knowledgerepresentation and training for a Socratic controller with multiplelower-level classifier modules. As already discussed in reference toother Figures, one task of a Socratic controller as a Socraticcontroller is to estimate the reliability of the lower-level classifiermodules. This task of estimating the reliability of the lower-levelclassifier modules is itself a pattern recognition problem. One approachto the problem of combining the results of the lower-level classifiermodules is to treat it as a problem in non-linear regression.

FIG. 12 is a flowchart of one embodiment of a Socratic controller toaccomplish these tasks.

An underlying concept in this one embodiment is that in a system withmany classifier modules, certain classifier modules will work well incertain regions of the data space and other classifier modules will workwell in other regions of the data space. For example, a classifiermodule that has been based on human design effort will often performwell on cases that are like those that have been explicitly consideredby the designer but may perform less well on some of the cases that havenot been explicitly considered in the design. As another example, aclassifier module that has been trained primarily on samples from agiven environment may not perform as well on data obtained from adifferent environment. In many applications this property will occurnaturally. In one embodiment of the invention, this property will befurther enhanced because each classifier module will be specificallytrained to do well in certain assigned regions of the data space and newspecialized classifier modules will be automatically created to improveperformance in regions of the data space in which existing classifiermodules do not perform adequately.

Block 1210 trains a classification of the data space into distinctregions. In the one embodiment, this classification is done by adecision tree, which is a process well known to those skilled in the artof pattern classification. A classification of the data space is aclassification that determines a partition of the data space. In the oneembodiment, the partition of the data determined by the decision tree isfurther optimized by the process shown in FIG. 11.

Block 1220 trains the lower-level classifier modules of the Socraticcontroller being trained. In one embodiment, the lower-level classifiermodules are trained for data within a given region of the data space.That is, in this embodiment each lower-level classifier module istrained to have a set of models specific to the given region of dataspace, by training on data only from that region.

Block 1230 selects a subset of active lower-level classifier modules. Inone embodiment, the Socratic controller performs a higher-levelclassification task modeling the performance of the lower-levelclassifier modules. The subset of lower-level modules that are estimatedas the highest performing lower-level modules in the given region ofdata space is selected as the active subset. The set of activeclassifier modules will be different for different regions, even for agiven Socratic controller.

Block 1240 trains the weights for combining the scores returned by thelower-level classifier modules. In one embodiment, the weights arecomputed by estimating a regression function associated with thehigher-level classification task in which the Socratic controllerestimates the performance of the lower-level classifiers for the givenregion of data space. A different regression function of combiningweights is computed for each region.

Block 1250 tests whether blocks 1220 through 1240 have been executed foreach of the regions in the data space. If not, control returns to block1220 to train another region. When all the regions have been done, theprocess exits.

FIGS. 13 and 14 relate to methods for building a decision tree. Decisiontree building may be applied to recognition on any kind of patterns. Toprovide a illustrative examples for some of the steps in the processesshown in FIGS. 13 and 14, examples will be draw from the recognition ofphonemes in continuous speech. Phonemes are the basic sound units inspeech, roughly corresponding to letters in written test. These examplesfrom the recognition of phonemes are provided only as illustrativeexamples and not as imposing any limitations or restrictions on theembodiments described or on the invention.

FIG. 13 is a flowchart of one method for building a decision tree suchas could be used to classify regions of the data space in the embodimentof block 1240 of FIG. 12.

Block 1301 selects a leaf node (a node without any branches). Theprocess begins with an empty tree, that is, a tree with a single nodeand no branches. The single node is the root node. Initially, since ithas no branches it is also a leaf node.

There are well-known algorithms for building classification andregression trees. These well-known algorithms may be used to build adecision tree for partitioning the data space for a Socratic controller.However, the purpose for partitioning the data space is not the normalobjective of a classification problem. One embodiment of the inventionuses a non-standard algorithm, adding blocks 1302 and 1307 to a standardtree building algorithm.

Block 1302 selects an objective for the node selected by block 1301. Ina standard binary classification problem, the objective of each node intypical tree-building procedure is simply to maximize the decrease inentropy that is achieved by splitting the data according to the datatest that is selected for the node. In building a tree for partitioningthe data space for a Socratic controller, the objective of each node isless well defined.

Overall the purpose of the tree is to partition the data space such thatfor each region of the space the reliability of each lower-levelclassifier module is relatively constant, whereas the reliability of thelower-level classifier module may vary from one region to another.Rather than having a single objective, this decision tree has anobjective for every one of the lower-level classifier modules controlledby the Socratic controller. In one embodiment, these multiple objectivesare addressed by having different objectives be optimized at differentnodes within the tree.

Block 1302, therefore selects a particular subset of the lower-levelclassifier modules. The tentative objective for the selected node thenbecomes to maximize the amount of information that is obtained about thereliability of the selected subset of classifier modules by the datasplit that is made at the node. By way of illustration, one embodimentof a phoneme recognizer might have a separate classifier module as adetector for each phoneme. In this embodiment, an example of a subset ofthe classifier modules would be the set of classifiers that detectvowels. Another example of a subset would be the set of classifiers thatdetect voiceless sounds.

Block 1303 selects a candidate question. A question is some test on thedata that splits the data at the node into two complementary subsets.For one embodiment of a phoneme recognizer, the data to be recognizedwould be the result of signal processing the speech waveform usingtechniques such as a Fourier transform. An example data feature might bethe magnitude of the Fourier transform of the speech signal at a givenfrequency for a given placement of a time window within the speechutterance. An example question in this embodiment would be whether themagnitude of this Fourier feature exceeds a certain specified value.Another example question would be whether the magnitude of the Fouriertransform at a particular frequency is greater or less than themagnitude at the same frequency in the next time window. Another examplequestion would be whether the magnitude is a local maximum in frequency,that is, whether it is greater than the magnitude at the two adjacentfrequencies, one lower frequency and one higher frequency.

Block 1304 optimizes parameters if the selected question has adjustableparameters. For example, one type of question is a linear discriminantfunction. In one embodiment of the phoneme recognizer example, a lineardiscriminant function might be constructed to discriminate vowels fromfricatives. The parameters of this discriminate function would beoptimized for the discrimination task before measuring the performanceof the question on the node splitting task in the tree building process.Another form of question compares the value of some function of the datawith a decision threshold value. In one embodiment of the phonemerecognizer example, an example of this form of question would be thecomparison of the magnitude of the Fourier transform at a particularfrequency of a particular placement of a time window of the speech to aspecified value. The specified value would be adjusted to optimize theperformance on the node splitting performance measurement to be appliedin block 1305.

Block 1305 compares the performance of the selected question, with itsoptimized parameters, to the performance of previous trial questions. Inone embodiment, the performance of a selected question is the amount ofmutual information or decrease in entropy that is achieved by therefined partition based on the question compared to the partitionwithout the question. That is, in this one embodiment the performance ofa given question (after optimizing parameters) is measured by the amountof decrease in the function i(N) given byi(N)=−Σ_(j) P(w _(j))log₂ P(w _(j)),where P(w_(j)) is the fraction of data samples at node N that are inclass w_(j).

Block 1306 selects the best performing question among those evaluated sofar.

Block 1307 applies a stopping criterion to test whether additional trialquestions should be evaluated. If so, control returns to block 1303. Ifnot control proceeds to block 1308.

Block 1308 applies a criterion to test whether other objectives shouldbe evaluated for the selected node. If so, control returns to block1302. If not, control proceeds to block 1309.

Block 1309 selects the best objective and the best question for thatobjective. It associates the selected question with the selected node.It applies the question to split the training data. Two new branchesleaving the selected node, each with a new leaf node, are created. Thedata that answer the selected question one way follow the left branchand the data that answer the selected question the other way follow theright branch. For example, in one embodiment of the phoneme recognizerfor a particular selected node the best objective in terms of the nodesplitting performance measured in block 1305 might be the objective ofseparating the vowel detectors from the fricative detectors. The bestquestion for that objective might be the ratio of the magnitude of theFourier transform summed across all the high frequencies compared to themagnitude of the Fourier transform summed across all the lowfrequencies. In this example, the data samples with greater magnitude inhigh frequencies would go down one branch, say the left branch. The datasamples with greater magnitude in the low frequencies would be sent downthe right branch. That is, the high frequency data samples would bepresented as samples to the node at the end of the left branch and thelow frequency data samples would be presented as samples to the node atthe end of the right branch.

Block 1310 applies a stopping criterion to test whether thetree-building process is complete. In one embodiment, there a minimum isset for the quantity of data available at a node in order for the nodeto be selected in block 1301 as a node to be split. The tree buildingprocess is terminated if there are no more nodes to be split, or if someother stopping criterion, such as a maximum number of levels for thetree, is reached. If no stopping criterion is met control returns toblock 1301.

FIG. 14 is a flowchart of one process for developing questions to beused in a multiple class decision tree, such as the decision tree usedin one embodiment of a Socratic controller to partition the data spacefor estimation of reliability of the lower-level classifier modules. Inone embodiment, this will be a source for the questions selected inblock 1303 of FIG. 13.

For the reliability estimation in a Socratic controller, the classes tobe discriminated are implicit rather than explicit. For the data at anynode in the decision tree there will be some lower-level classifiermodules whose performance varies substantially across different regionsof the space. For example, suppose in one embodiment of a phonemerecognizer that the preceding node has been split based on a comparisonof high frequency energy with low frequency energy in order to satisfyan objective of separating vowels from fricatives. For the exampleconsider the node for which the data samples have more high frequencyenergy. Although fricatives generally have more high frequency energythan vowels, there is much more high frequency energy in some fricativesthan in others. The fricative /s/ has the most high frequency energy.The fricatives /sh/ has a considerable amount of high frequency energy,but it is mostly at a lower frequency than for the /s/. The fricatives/f/ and /th/ have less energy overall and the energy is spread out overboth low and high frequencies. Thus in the illustrative example it islikely to be the case that the performance of the lower-level detectorsfor /f/ and /th/ varies depending on the data even though the data hasalready been selected to have more high frequency energy. On the otherhand the performance of the /s/ detector might be high for most of thedata samples that come to this node. For lower-level classifiers that donot already classify the data consistently, the objective is to ask anadditional question to divide the data space such that for each of thelower-level classifier modules the performance will be relativelyconstant in each of the two divisions of the space. For lower-levelclassifiers whose performance does not vary much across the undividedspace, whether that performance is good or poor, it doesn't matter verymuch where the space is divided.

Block 1401 chooses a pair of classes to discriminate. In oneimplementation of a Socratic controller, the choice in block 1401 is ofa particular lower-level classifier module. The two classes to bediscriminated are the region of good performance by that particularlower-level classifier from the region of poor performance by thatparticular lower-level classifier. Carrying forward the example above,the chosen lower-level classifier might be the /f/ detector. The pair ofclasses to be discriminated is the data on which the /f/ detector makesa correct decision (that is, it decides correctly whether or not a givendata sample is an /f/) versus the data on which the /f/ detector makesan error.

Block 1402 trains a discriminator for the two class problem. There aremany well-known techniques for training a two-class discriminator. Inone embodiment, a simple form of discriminator is used in which a testis made on only one data feature. In this one embodiment, the trainingis done by trying each data feature, and for each data feature creatinga discriminator by testing whether the value of the feature is greateror less than a specified threshold value. The threshold value is set tooptimize a data splitting criterion, such as the one described inreference to block 1305 of FIG. 13.

Block 1403 assigns other classes to the target partition. In oneimplementation of a Socratic controller, the performance of thelower-level classifier is measured on the two regions of the divisioncomputed in block 1403. If the performance of a particular lower-levelclassifier is significantly better in one of the two divisions, thenthat division is assigned to the class indicating good performance bythat particular lower-level classifier and the opposite division isassigned as a target class the indicator of poor performance by thatparticular lower-level classifier. Continuing the above example, it maybe that the /th/ detector performs well on data for which the /f/detector performs well and performs poorly on the data for which the /f/detector performs poorly. Then the /th/ detector would be assigned tothe same class as the /f/ detector. This good-class versus poor-classassignment is made for each lower-level classifier for which theperformance varies significantly between the two parts of the division.In the example, it might be that many of the vowel detectors performuniformly poorly on both of the divisions determined by the /f/ detectorand that the /s/ detector performs well on both divisions. In oneembodiment, these lower-level classifiers that perform uniformly on thetwo divisions are not assigned to either class, regardless of whetherthe uniform performance is good or poor. Lower-level classifiers thatperform poorly at a given node in the decision tree will be primecandidates as objectives in nodes further down the tree.

The classification assignments made by block 1403 define a newdiscrimination problem. In this discrimination problem, each data pointis targeted to be assigned to the division that has the most agreementswith the good-class, poor-class target values.

Block 1404 trains a discriminator for this new discrimination problem.

Block 1410 checks whether a pairwise test is to be made on the qualityof the discriminator trained in block 1404. In one embodiment of aSocratic controller, such a pairwise test is always to be used. If apairwise test is not to be used, then the process proceeds to block1407, which uses a non-Socratic multi-class objective measurement. Inone embodiment, the multi-class evaluation is performed by a Socraticagent as described with reference to FIG. 5, with more than two decisionalternatives in block 510 of FIG. 5.

If a pairwise test is to be conducted, control proceeds to block 1405.Block 1405 sets up a Socratic agent to compare the performance of thediscriminator trained in block 1404 to the best discriminator previouslyfound. The two candidate discriminator form a paired-model allele. TheSocratic agent performs a sequential decision test on this paired-modelallele as shown in FIG. 5.

Block 1406 selects the better of the two discriminators evaluated inblock 1405, which now is the best discriminator which has been found sofar.

Block 1408 checks whether a stopping criterion has been met. If not,then control returns to block 1401 and another pair of classes ischosen. In one embodiment of a Socratic controller each candidate pairof classes is associated with a particular lower-level classifiermodule, so the number of possible choices in block 1401 is limited tothe number of such lower-level classifier modules.

FIG. 15 is a flowchart of a process for choosing which lower-levelclassifier modules to train when training a collection of lower-levelclassifier modules controlled by a Socratic controller. For thistraining, there is a set of training data and a set of practice data,which in this context is also called evaluation data.

Block 1501 obtains a training sample, that is a training samplecomprising a data item and an associated label.

Block 1502 obtains an evaluation or practice sample. In one embodiment,the labels for the training data and the practice data will already havebeen corrected by using delayed decision training with label correct asshown in FIGS. 3 and 6.

Block 1503 obtains an estimated answer for the evaluation sample. Theestimated answer is simply the label associated with the evaluationsample. It is called an estimated answer here to emphasize the fact thatit is not assumed that the labels for the practice data have beencreated or verified manually. Rather they may be automatically generatedlabels for data that is originally unlabeled or only partially labeled.The process of FIG. 15 is as tolerant of labeling errors in the practicedata as is the delayed-decision training process for Socratic agents.

Block 1504 controls the loop that evaluates lower-level classifiermodules as candidates to be trained using the training sample obtainedin block 1501. In one embodiment, the Socratic controller first selectsa subset including the lower-level classifier modules that the Socraticcontroller estimates as the most likely to improve performance bytraining on particular training sample. Block 1504 is positioned in theflowchart based on its role of controlling the loop through all selectedlower-level classifier modules. In one embodiment, the selection dependsonly on the data features of the training sample, so the subsetselection can be done outside the loop beginning at block 1505. In oneembodiment, each lower-level classifier module is trained on the giventraining sample and the amount of change in the models in each module ismeasured. A subset of the modules with the greatest change in theirmodels is selected.

For each selected lower-level classifier module, block 1505 trains themodel for the given lower-level classifier module and creates amatched-pair allele of models with and without training on the trainingsample obtained in block 1501.

Block 1506 basically follows the procedure of delayed decision training.However, rather than making a decision to train or not on the givenevaluation sample, block 1506 merely records the information as to howmuch improvement in performance is achieved for the given lower-levelclassifier module. It accumulates such performance measurements acrossall passes through the loop from block 1502 to block 1508.

Block 1507 completes the loop of selected lower-level classifiermodules. For each selected classifier module, further performance datahas been accumulated, but the decision of which lower-level module ormodules to choose will be based on multiple evaluation samples, and ispostponed to block 1509.

Block 1508 applies a stopping criterion to test whether enough evidencehas been accumulated to select which lower-level classifier module orclassifier modules should be chosen to train on the training sampleobtained in block 1501. If the stopping criterion is not met, controlreturns to block 102 to obtain another evaluation sample. Otherwisecontrol proceeds to block 1509.

Block 1509 chooses the classifier module that achieves the mostimprovement by training on the given training sample, or chooses a smallnumber of the most improved classifier modules. The control returns toblock 1501 to obtain another training sample. This training process isan on-going process that in some embodiments may proceed indefinitely.Because block 1509 chooses only one or a small number of classifiermodules to be trained on any given sample, the lower-level classifiermodules learn to specialize and become more diverse. Furthermore, as theprocess continues all performance measurements are made in the contextof the performance of the composite result computed by the Socraticcontroller. Therefore, the training selection is chosen to optimize thiscomposite performance, not the performance of any individual lower-levelclassifier module.

FIG. 16 illustrates how a Socratic agent can empirically adjust a systemcontrol parameter. Note that a system control parameter can beempirically tuned by simple hill-climbing based on measured performanceif a sufficient quantity of labeled practice data has been set aside.The procedure illustrated in FIG. 16, however, is more robust and anunlimited quantized of semi-supervised evaluation data may be used. Ifpractice data is available, then either non-Socratic hill-climbing basedon performance on practice data, or the procedure of FIG. 16 may beused, on a case-by-case basis at the option of the system designer.

As an illustrative example, consider an image recognition system. Forthe example, assume that the image recognition system has a collectionof low level classifier modules that detect components of images andfeatures of objects within an image, such as edges, corners, texture,shading, reflectivity, and do forth. Further assume the imagerecognition system has a number of intermediate level classifier modulesthat receive as input the results output by the low-level modules.Assume that these intermediate-level modules all try to segment andclassify objects within the image. For the purpose of this illustrativeexample consider a Socratic controller that has this set ofintermediate-level modules as its lower-level classifier modules. Forpurpose of the example, call the intermediate-level modules that are thelower-level modules for the Socratic controller the “given modules.”Assume that the given modules use a variety of techniques to identifydifferent kinds of objects. For example, assume that some of the givenmodules specialize in recognizing that a given portion of an image is aface. Assume that other modules specialize in distinguishing the face ofone person from the face of a different person. Assume that some modulesspecialize in recognizing geometric shapes and that others specialize inrecognizing animals. More generally assume that the Socratic controlleris associated with a wide variety of given modules that use a widevariety of pattern recognition techniques.

Consider now the training of the Socratic controller and the givenmodules, which are in this context its associated lower-level modules.One embodiment of a process for training the higher-level classifiermodule on the higher-level pattern-classification problem within theSocratic controller was shown in FIG. 9. This embodiment is notdependent on the particular type of lower-level pattern classificationbeing done by the associated lower-level classifier modules, and willnot be discussed further in this particular illustrative example.

However, in this example, the given modules also need to be trained,with the assistance of the Socratic controller. One embodiment for suchtraining has been shown in FIG. 15. The key steps of the trainingprocess are a follows: First a collection of classifier modules isobtained. In the example, these modules are the intermediate-level imageclassifier modules, but they are referred to as lower-level modulesrelative to the Socratic controller. The Socratic controller optionallyperforms a higher-level pattern recognition process to select thelower-level classifier modules most likely to improve from training on aparticular sample obtained in block 1501. In any case, the Socraticcontroller performs a higher-level pattern recognition task as part ofthe recognition, in selecting the active subset of lower-levelclassifier modules and/or in combining the results of the lower-levelclassifier modules into a composite result, as shown in FIG. 10.

In the training process, the Socratic controller actively controls thetraining of its associated lower-level classifier modules. The overalleffect of the process shown in FIG. 15, is that only one or a very smallnumber of lower-level classifier modules is selected to be trained onany one training sample. Training different lower-level classifiers ondifferent samples will tend to increase diversity even if the assignmentof training samples to modules is made randomly or is made based on somecriterion that is not directly related to diversity. However, in theprocess shown in FIG. 15 the training assignment are made to directlyincrease the end objective, which is improved recognition performance.Diversity is increased directly in proportion to the extent that thediversity contributes to improved recognition performance.

In terms of the illustrative example, the example image recognitionsystem has many different kinds of intermediate classifier modules,which are the lower-level modules for the given Socratic controller.Consider a specific training example of an image that includes aperson's face. The subset selection among the classifier modules wouldselect a subset composed mostly of classifier modules that eitherrecognize that a face occurs in the image or that distinguish one facefrom another. The selected subset is trained on the given trainingsample. In one embodiment the trained version is made the inactivemember of a linked allele. In one embodiment, the image recognitionsystem proceeds with its normal recognition tasks. The data to berecognized is made into practice data by assigning labels based on theautomatic recognition plus human-supplied error correction, if anyhappens to be available. From this practice data, any practice samplesthat involve the models in the linked allele may be used for evaluatingthe comparative performance of the training of the respectivelower-level classifier modules.

Assume that a particular one of the lower-level classifier modules hasnever been trained on a face that is similar to the face in the giventraining sample. Assume that another one of the lower-level classifiermodules has been trained on a large number of faces that are somewhatsimilar but that have a high degree of variability among them. It cannotbe determined from the given characteristics which of the describedlower-level classifier modules will benefit the most from being trainedon the given training sample. More importantly, just from thesecharacteristics it cannot be determined which choice will most improvethe overall recognition performance.

In particular, training the lower-level module that has never seen asimilar face might significantly improve is performance on other similarfaces, whereas training the other lower-level module might make lessdifference since for that module it would only be one more example amonga large number of similar examples. However, if the first module hasnever seen a similar face, it might have learned to specialize in otherkinds of faces for which the given training sample would be an outlier.Forcing this module to train on the given training sample might degradeits models (depending on internal details that will be ignored for theexample). It might further be the case that, if the first module hasspecialized in other kinds of faces, then not training it on giventraining sample will not hurt overall system performance because othermodules, including the second described module handle faces like the onein the given training sample. This example indicates that it might bedifficult to decide which lower-level modules should be trained on agiven training sample.

The Socratic controller actively controls the training process. Itanswers the question of which lower-level classifier modules to train ona given training sample by a kind of delayed decision testing. Theprocess is robust against labeling errors in both the training data andin the practice/evaluation data, because decisions are based on theaccumulation of statistically significant evidence across a substantialplurality of practice samples.

In reference to FIG. 16, block 1601 selects a system control parameter.A system control parameter is a scalar-valued parameter that controlsthe process flow, such as the amount of data to accumulate beforeapplying the stopping rule in block 310 of FIG. 3 or block 409 of FIG.4. More generally, any scalar-valued parameter that does not change ordepend on the particular data being analyzed in a given data item may betreated as a system control parameter and optimized by the procedureillustrated in FIG. 16.

Block 1602 creates two versions of the system or subsystem under study.In one version, the selected parameter is incrementally decreased. Inthe other version the selected parameter is incrementally increased. Thedefault value for the amount to increment a parameter is itself a systemcontrol parameter, which may be optimized by the process of FIG. 16. Fora given control parameter, the default increment value is adjusted bythe range or scale of the given parameter, unless all control parametersare normalized to the same scale (possibly by a non-lineartransformation), such as a scale of 0 to 1. If a particular controlparameter has already been processed as illustrated in FIG. 16, the sizeof its increment may be increased or decreased from the previous value,depending on the prior behavior. If testing of the given controlparameter has been stopped by block 1608 without the null hypothesisbeing rejected, then the increment may be increased from the size of theincrement used in the previous test. If there have been inconsistentdecisions among multiple previous rounds of testing, that is, ifsometimes the null hypothesis has been rejected in favor of increasingthe parameter and sometimes it has been rejected in favor of decreasingthe parameter, then the size of the increment may be decreased from itsprevious value.

Block 1603 obtains an evaluation sample and begins an evaluation loop.

Block 1604 obtains an estimated answer for the given evaluation sample.If a human-supplied or human-verified answer is available, then thatanswer may be used as the estimate. If a semi-supervised label isavailable, that may be used. Alternatively, a new automaticallygenerated answer may be obtained. If the given control parameter onlyaffects a single subsystem or a single classified module in amulti-module system, then the automatically generated answer may beobtained from recognition by the whole system. If the control parameteraffects the whole system, then either of two strategies can be used.Recognition can be performed by a collection of two or more completesystems and their consensus answer may be used. A strategy that may beused even when multiple systems are not available is to artificiallyrestrict the application of the perturbed value of the control parameterto a subset of the subsystems or modules. The parameter may then betested in the same way as a local parameter. The control parameter maybe independently tested on the complementary subset or separately oneach element of a partition of the subsystems. If the adjustments to thecontrol parameter are inconsistent in different subsets, either theadjustment can be rejected as if the null hypothesis has been confirmed,or the control parameter can be partitioned into local controlparameters tuned for each subset of subsystems or modules.

Block 1605 accumulates performance statistics comparing the performanceof the system with the two incrementally perturbed values of the controlparameter.

Block 1606 tests to see if the null hypothesis can be rejected at thespecified level of statistical significance. The null hypothesis is thatthere is no net performance difference between the two system versionswith perturbed values for the given control parameter.

If the null hypothesis is rejected, then the process goes to block 1607,where the better parameter value is chosen. Then the process returns toblock 1602 to continue to optimize the selected control parameter.

If the null hypothesis is not rejected, control goes to block 1608,which checks to see if a stopping criterion has been met. If thestopping criterion has been met, then the null hypothesis is accepted.The parameter is left at its unperturbed value and the evaluation thegiven parameter is halted until the parameter is again selected by block1601.

The present invention enables a pattern recognition system with a largenumber of both independent and related classifier modules. FIG. 17 is aflowchart of a process that is used in one embodiment to automaticallycreate classifier modules.

Block 1701 chooses a decision point. This may be almost any kind ofdecision point. For example, it could be a system design decision, suchas what training algorithm to use. With regard to clustering, forexample, it could be a decision of what clustering algorithm to use, orit could be a decision of what threshold to use in deciding to merge toclusters. However, it could also be a decision made by a program at astep within the clustering algorithm. In any of the algorithms withstopping rules, there is a whole range of potential decisions atdifferent values of the stopping criterion. For the delayed-decisiontraining procedures shown in FIGS. 3 and 4, there is the possibledecision to not choose one of the two alternatives, but rather to acceptboth. Any choice of a control parameter such as optimized in FIG. 16could instead be represented as a decision point with multiplealternative values of the control parameter.

Block 1702 creates a lower-level classifier module for each decisionalternative at the decision point. It is preferable that theseclassifier modules be diverse. In particular, it is valuable if eachclassifier module makes mistakes in different situations than the otherclassifier modules. The goal of achieving diversity in turn means thatthere is a preference for choosing decision points in block 1701 thatwill result in relatively large differences in behavior in theclassifier modules arising from the decision alternatives. However, itis not essential that classifier modules have great diversity when firstcreated in block 1702 because the Socratic controller controls the jointtraining of the collection of associated classifier modules so as toincrease the diversity among the lower-level classifier modules.

Block 1703 assigns the lower-level classifier modules created in block1702 to a single Socratic controller. These new classifier modules mayeither be assigned to an existing Socratic controller, or a new Socraticcontroller may be created, initially with just the newly createdclassifier modules as lower-level classifier modules.

Block 1704 checks whether the process of creating new classifier modulesshould continue. If so, control returns to block 1701.

FIG. 18 is a flowchart of one embodiment of a process by which newclassifier modules may be created as an extension of the process ofcreating a Socratic agent.

Block 1801 creates a linked-model Socratic agent.

Block 1802, rather than setting up a delayed-decision trainingevaluation, accumulates and measures statistics of co-occurrence, thatis whether or not the linked models make errors of the same data sample.The co-occurrence statistics measurement might be in addition to thedelayed-decision training, especially for a Socratic agent that wouldhave been created anyway for the purpose of delayed-decision training.

Block 1803 tests the diversity between the different versions of theclassifier module with the plurality linked-model sets. In oneembodiment, the diversity is measured by the extent to which the errorsmade by each pair of linked models are diverse, If there is sufficientdiversity, process proceeds to block 1804, otherwise, it returns toblock 1801. In one embodiment, the diversity is estimated from thecounts of the number of times one of two models makes an error andwhether the other model makes an error on the same data sample. Let E₁be the number of times that the first model makes an error on a datasample on which the second model does not make an error. Let E₂ be thenumber of times that the second model makes an error on a data sample onwhich the first model does not make an error. Let E₁₂ be the number oftimes that both models make an error on the same data sample. Then inone embodiment, the diversity d is measured by the formulad=(E ₁ E ₂ −E ₁₂ E ₁₂)/(E ₁ +E ₁₂)(E ₂ +E ₁₂).

The diversity d will be in the range 0≦d≦1. The greater the value of d,the greater the diversity. Higher values of diversity correspond to agreater tendency for improved performance when combining the results ofmultiple classifier modules. In one embodiment, the models areconsidered diverse if d>−0.5. If the models are diverse, multiplemodules will be created in block 1804.

As an illustrative example to show the effect of diversity, consider aSocratic controller with three lower-level classifier modules. For thisexample, assume that each lower-level classifier module has aprobability of making an error of 0.01. In one case, assume that thethree lower-level classifier modules are completely non-diverse. Thatis, when any one of the three modules makes an error, the other twomodules make the same error on the same data sample. The pair-wisediversity is −1 for each pair of these modules. Clearly, in this casethe three non-diverse modules together have no greater value than anyone of them alone. In a second case, assume that the three lower-levelclassifier modules are completely diverse; that is, assume that wheneverone of the three modules makes an error on a data sample, the other twomodules classify that data sample correctly. Assume that the method forcombining the results of the three classifier modules is to use majorityvote. That is, if any two of the classifier modules agree, then theiragreed answer is selected as the combined answer. It can be seen thatthis combined answer will never be an error. Of course, a perfectdiversity of d=1 is unrealistic. However, the greater the diversity thebetter a set of modules will be able to correct errors in creating itscombined result.

Block 1804 creates a plurality of independent modules. In each of thesemodules, a different one of the diverse models is made active.

Block 1805 checks whether creation of new classifier modules is tocontinue.

In one embodiment, the process of creating new modules may be done aspart of an on-going process of delayed-decision testing by Socraticagents. In this embodiment, the collection of statistics of correlationof errors is simply added to the collection of evidence to accept orreject the null hypothesis. In another embodiment, correlationstatistics may be collected for any set of linked models, whatever thesource of the models and whether or not the linked models are beingtested by a Socratic agent. This one embodiment includes the followingsteps:

-   -   1) Create a linkage between a plurality of models. Interpret        “model” in the broadest sense. Each “model” in the set of linked        models could be a composite model that includes an entire set of        simpler models. Each “model” could also be an entire classifier        module, including the processing software. In one embodiment, an        operational requirement is that the linkage be such that one        model (or module) of the plurality of models be active at a time        and that the linkage provide a mechanism by which the active        model may be switched so that a different model become active.    -   2) Collect evidence of the degree to which the errors made by        each pair of models in the plurality of linked models is        diverse.    -   3) If two or more of the linked models are sufficiently diverse,        create a set of modules such that in each module a different one        of the diverse linked models is active.    -   4) If the process of FIG. 18 is continued indefinitely, the        number of modules might grow beyond a reasonable number. In one        embodiment, the plurality of linked modules are also tested to        see if any of the plurality of models should be deleted. One        embodiment of this testing is to test each of the plurality of        models using the process shown in FIG. 4, beginning with block        421.

FIG. 19 is a flowchart of the process of a form of semi-supervisedtraining of a simplified pattern recognition module or classifier moduleby a more computation intensive classifier module.

Block 1901 obtains a first classifier. An example of a classifier is alarge vocabulary spoken word recognizer based on modeling the acousticsof each word as a hidden Markov process and computing the match of eachspoken word model by a process of dynamic programming.

Block 1902 uses the first classifier obtained in 1901 to automaticallylabel some set of data.

Block 1903 sets aside some of the labeled data as training data.

Block 1904 sets aside some of the labeled data as practice data.

Block 1905 obtains a simplified classifier. By way of example, asimplified classifier for a large vocabulary word recognizer could beobtained by matching only the first three phonemes of each word againsta fixed segmentation of the data without dynamic programming. In oneembodiment, the simplified classifier will attempt to approximate theperformance of the first classifier. However, it will do so with fewercomputational resources. That is, it will use less computation timeand/or less memory. The simplified classifier will completely achieveits objectives if it makes exactly the same mistakes as the firstclassifier.

In the example large vocabulary word recognizer, the simplifiedclassifier is used as a first-stage selection process. Based on thematch scores computed by the simplified classifier, a subset of thevocabulary is selected such that the match for the more computationallyexpensive first classifier only needs to be performed for a subset ofthe full vocabulary. In one embodiment of a word recognizer for a onehundred thousand word vocabulary, the simplified classifier might beused to select a subset of only around one thousand words that need tobe matched using dynamic programming for the hidden Markov models. Notethat the simplified classifier only introduces a new error if the bestmatching word in the first classifier is correct and if that bestmatching word is not among the one thousand best matching words asestimated by the simplified classifier. Note that to train thesimplified classifier it is not necessary to know the correct word. Itis sufficient to know the best matching word as computed by the firstclassifier. In training and practice, the performance of the simplifiedclassifier is measured by whether the best matching word as computed bythe first classifier is among the one thousand best words as estimatedby the simplified classifier.

Block 1906 performs delayed-decision training of the simplifiedclassifier as shown in FIGS. 3, 4, and 5 using the training data andpractice data that has been automatically labeled by the firstclassifier. Because the goal of the simplified classifier is merely toapproximate the first classifier without introducing any new errors, itis as if the labels on the training data and practice data are correctby fiat.

FIG. 20 is a flowchart of a process of sharing knowledge amongclassifier modules.

Block 2001 obtains multiple classifier modules.

Block 2002 chooses one of the classifier modules.

Block 2003 performs communicable learning for the chosen classifiermodule. This learning could just be learning that takes place in thenormal operation of the system that contains the chosen classifiermodule. On the other hand, it could be extra learning that is undertakenespecially for the purpose of discovering communicable new knowledge.Communicable learning is the learning of some piece of knowledge thatcan be transferred into the knowledge representation of other classifiermodules.

One-shot learning, in which a new entity of some kind is created,inherently tends to be communicable. Because the new entity didn'tformerly exist even in the chosen classifier module there is no priorknowledge that needs to be in place to identify the same entity inanother classifier module. Rather the new entity is simply added to thesecond knowledge in the same way that it was added to the chosenclassifier module. If the new classifier module uses different featuresin its input data, one-shot learning can be used to create the new modelin the new classifier module.

Structural learning is generally communicable between classifier modulesthat share a common structure. Structural learning is learning changesin a structure for pattern recognition, such as adding or deleting anarc to a graph, or additions or deletions from a finite collection, suchas adding or deleting a cluster to a collection of clusters or adding ordeleting a component distribution in a mixture of probabilitydistributions.

Correction of a label through feedback from delayed-decision training iscommunicable knowledge to any classifier module that uses the samelabeled sample, either for training or as practice data.

Depending on the particular application other learned knowledge iscommunicable if the sharing classifier modules have a shared knowledgerepresentation and the new knowledge is represented as a discrete changeand not merely as the value of a parameter for which the interpretationof the value is dependent on the particular context. For example, in twoclassifier modules for acoustic models in speech recognition, acousticfeature measurements that depend on the particular signal processingwould generally not be communicable to classifier modules that usedifferent signal processing. However, estimates of the absolute orrelative position of articulators in the vocal tract would have the samemeaning regardless of the method by which the estimate is made and,hence, would generally be communicable. Regardless of the application,one-shot and structural learning will generally be communicable to somenew classifier modules.

In speech recognition, for example, adding a new word to the vocabularyor adding or deleting a pronunciation to the dictionary is communicable.Adding or deleting an allophone of a particular phoneme is communicable.Representing that a particular allophone is possible or impossible in agiven context is communicable.

Block 2004 selects one or more other classifier modules. For structurallearning, the selection would be limited to other classifier modulesthat share the structure to be modified. For example, in the addition ordeletion of an arc or node in a graph of an acoustic model for a phonemein a speech recognition system, the selection of other classifiermodules would be limited to modules that use the same graph before theaddition or deletion.

Block 2005 tests the candidate knowledge in the selected otherclassifier modules. In the one embodiment, this testing is done bydelayed-decision testing as shown in FIG. 3, 4 or 5, respectively asappropriate to the particular form of knowledge change.

Block 2006 feeds back the performance results to the originatingclassifier module that was chosen in block 202.

Block 2007 decides whether to adopt the new knowledge on asemi-permanent basis, that is until a later decision is made to changethe knowledge again, possibly changing it back. To permanently adopt theknowledge, an acceptance criterion must be met. In one embodiment, theacceptance criterion would be more conservative than for adopting newknowledge just in a single classifier module. In particular, theacceptance criterion would require that a substantial majority of theperformance feedback results from other classifier modules be positive.

Block 2008 adds the knowledge to other classifier modules. Generally theother classifier modules will not be lower-level classifier modules ofthe same Socratic controller as the originating classifier module. Infact, the other classifier modules do not even need to be part of thesame instance of the recognition system. For example, in a widelydistributed commercial speech recognition system, the knowledge of a newword in the vocabulary or of a new pronunciation in the dictionary couldbe shared across a large number of systems.

With a very large number of classifier modules or a very large number ofsystems sharing knowledge, one embodiment would first select only amoderate number of other classifier modules in block 2004. If thedecision in block 2007 is to adopt the candidate knowledge, controlwould return to block 2004 to select a larger set of other classifiermodules. With classifier modules distributed among a large number ofsystems, this process might be repeated several times with the number ofsharing classifier modules growing each time there are positiveperformance feedback results.

When the other classifier modules do happen to be other lower-levelclassifier modules of the same Socratic controller, block 2008 performsextra testing before adding the new knowledge to a particularlower-level classifier module. The testing in block 2005 is to check thevalidity in other contexts of the candidate knowledge. This validity canbe checked by the performance of the other classifier module inisolation. However, for the lower-level classifiers of the same Socraticcontroller it is desired that the lower-level modules exhibit diversity.Therefore, before adding the knowledge to a lower-level classifiermodule the performance of the new knowledge is tested in the context ofthe full Socratic controller with the new knowledge added to theoriginating classifier module and any the selected other classifiermodules.

As one embodiment, the process of FIG. 20 may be described by thefollowing steps;

1) obtain multiple classifier modules (possibly hundreds or thousands),

2) obtain a communicable model, either a new model or one that has beenmodified,

3) transmit the communicable model to at least one other classifiermodule,

4) in any classifier module receiving a transmitted model, test thecomparative performance of the receiving module with and without the newmodel, and make the better performing version the active model in thereceiving module,

5) transmit back the comparative performance information to theoriginating module,

6) if the comparative performance results are good, select a larger setof receiving modules and repeat steps (3) through (6). If thecomparative performance results are not good, then the transmittedcommunicable model did not significantly improve performance in thecontext of the receiving modules. This can happen, for example, if thereceiving modules already have other models that make the transmittedmodel redundant. In one embodiment, if a sufficient number of receivingmodules fail to get significantly improved performance, then the processis stopped and steps (3) through (6) are not repeated. However, thetransmitted model may still be used in its original module and any othermodules in which it has significantly improved performance. Over time,the models that will have been transmitted to the greatest number ofmodules will be those models that consistently improve the performanceof most of their receiving modules.

Further comments may be made regarding steps (1) and (2). In particular,in one embodiment multiple classifier modules may be obtained byactively creating them. In addition, new models may be created from thealternatives at any kind of decision point, not just a decision pointinherently involving models, and new modules may be created to containthese new models. In one embodiment, a model or a set of models may bemade communicable by writing a software wrapper to interpret the modelsin a new system environment and transmitting the entire resultingmodule. In one embodiment, the multiple modules may be contained inmultiple recognition systems. The transmission of an entireencapsulating module may facilitate the transmission of a model or modelset from one system to another and its utilization in the receivingsystem.

A very important aspect of this invention is the concept ofnon-determinism, in the sense of delaying or avoiding decisions in orderto avoid wrong decisions that would degrade performance. In particular,processes that have already been described embody some kinds ofnon-determinism. Both FIG. 3 and FIG. 4 illustrate a process by which adecision was delayed indefinitely based on sequential decision theory,accumulating more evidence until a decision could be made based on astatistically significant amount of evidence.

Another method for achieving non-determinism provides one embodiment forobtaining multiple classifier modules, as specified in block 2001 ofFIG. 20. This non-determinism method is to avoid choosing one method orone model by choosing “all of the above.” This “choose all” methodologyresults in the creation of multiple classifier modules that representdifferent methods of trying to do the same classification task. Inparticular, in designing a pattern recognition system, there are manydecisions in which a trade-off must be made. One embodiment ofnon-determinism creates multiple modules and avoids these designtrade-offs.

For example, one kind of processing may be better at recognizing certainpatterns, but a different kind of processing may be better atrecognizing certain other patterns. As another example, one kind ofprocessing may be more tolerant of certain kinds of variability ornoise, but a different kind of processing may be more tolerant of otherkinds of variability. Even in the automatic evaluation shown in FIG. 3or the automatic adjustment of control parameters shown in FIG. 16, thetwo versions being compared may make different kinds of errors than eachother. In all these cases, under the principle of avoiding decisions,two separate modules (which may be complete systems or subsystems) arecreated. Modules created in this way have different attributes and makeerrors in different cases, but they are all designed to work on the sameclassification problem.

Such a collection of modules is called a collection of cooperatingmodules. If modules are created using the principle of non-determinismor delayed decisions, in one embodiment they should be tested asillustrated in FIG. 4 (starting at block 421) to verify that they aremaking a sufficient contribution to performance to justify the resourcesthat they use.

FIG. 21 is a flowchart of a process for managing multiple evolvingsystems.

Bock 2101 obtains multiple systems. In a commercial product, themultiple systems could comprises all the systems that have been sold anddistributed and, connected through a network such as the Internet. In aresearch laboratory, the multiple systems could comprises manyexperimental systems with different designs. For purposes of this FIG.21, multiple systems that share the same communicable knowledge areregarded as a single system (perhaps more easily thought of as a singlesystem design realization). This is true even if the associated systemshave system-specific adaptations or transformations to their models.Each system may also have local knowledge that is not shared acrosssystems. The purpose of grouping together multiple systems with the samecommunicable knowledge is to be able to measure the performance of theknowledge independent of the environment of the individual system.

Block 2102 creates new systems by partial knowledge sharing. That is, itperforms knowledge sharing as shown in FIG. 20, except that for some ofthe other systems two versions of the system are created, one by sharingthe knowledge and one by not sharing the knowledge.

Block 2103 allows each system (or each group of associated systems) toevolve through continued training and learning. That is, each systemcontinues is normal process of recognition, adaptive training, one-shotlearning, Socratic agent supervised correction of training and practicedata, and so forth. Each system will be continually acquiring new dataand new knowledge. In one embodiment generally each system will beexposed to training data and practice data that is different from thetraining data and practice data available to other systems, althoughthere may be some amount of sharing and overlap of data.

Block 2104 measures the comparative system performance of each group ofassociated systems. This measures the performance of each system designrealization. For example, if a particular extra pronunciation has beenadded to the dictionary for some systems, then a group of associatedsystem with respect to knowledge of this pronunciation would be the setof systems for which the particular pronunciation has been added to thedictionary.

Block 2105 drops the lower performing system designs. In the case ofdistributed systems, an operational system is not discarded. The systemmerely has its communicable knowledge replaced by the knowledge from ahigher performing system and retains its local knowledge.

Block 2106 tests whether creating and testing of new systems shouldcontinue. In one embodiment, this evolution and improvement continuesindefinitely. Control is returned to block 2104 to obtain more systemsthat might have been created by other means. In any case, new systemswill be created by block 2102.

FIG. 22 illustrates a process of distributed computing and the jointtraining of multiple classifier modules distributed among multiplesystems. In FIG. 22, the classifier modules are merely called “modules”for brevity. In particular, FIG. 22 shows the process by which thediversity among the classifier modules is increased. It is assumed thatthere is a collection of loosely connected, cooperating systems, eachperforming the same pattern recognition process, but each having its ownstream of data and pattern recognition examples. Each system will alsomaintain its own set of models and trained modules, but the systems mayshare some of their models and modules, within the limitations of thecommunication bandwidth.

Block 2201 distributes a set of base modules to every system in a set ofcooperating systems. Two systems are shown for the purpose ofillustration, but an unlimited number of systems can work together usingthe process shown in FIG. 22. Block 2201 makes an identical copy of thebase models for every system in the set. The systems operate inparallel. There is a copy of the process from block 2202 to block 2207running simultaneously on each of the systems. From block 2201, controlpasses in parallel to the block 2202 in each of the cooperating systems.

Each system keeps one copy of the original base modules unmodified.However, each system also makes one or more copies of each of the basemodules to be adaptively trained with data collected by the localsystem.

As each system proceeds with its normal operation, it will collect datain block 2202. For example, in one embodiment of the invention in acommercially distributed product each copy of the product will collectdata to be recognized as the product is being used. If the productallows the user to correct recognition errors, each copy of the productwill also collect data about corrected errors, although this embodimentwould not assume that all errors have been corrected. This data will beused for training and evaluating the modules, and for creating newmodules.

Block 2203 in each system creates new modules by several mechanisms. Thecopies of the base modules begin to differ from the original basemodules as they are adaptively trained on the data obtained locally in agiven system. Additional new modules will be created in a similar wayfrom copies of modules received from other systems in block 2206 laterin the loop. New modules are also created from the outliers detected asin block 303 in FIG. 3 and tested as shown in FIG. 4. The process ofdelayed design decisions and non-determinism described above also isused to create new modules. All these new modules are adaptivelytrained, updated and evaluated as new data is collected in block 2202.

In addition to the normal performance evaluation, there is also anevaluation of the degree to which each module contributes to diversity,performed in block 2204. The task of block 2204 is to estimate thecontribution that a particular module makes to the total collection ofmodules in all of the cooperating systems. Therefore, for each module,block 2204 accumulates statistics measuring how well the particularmodule helps to correct errors that would otherwise be made by thecollection of unmodified base modules and the other modules that thegiven system has received from other systems (in block 2206 in previouspasses through the loop). That is, block 2204 measures how much a givenmodule improves the performance over the collection of unmodified modelsand models received from external sources.

Block 2205 selects a number of modules that contribute the most todiversity as estimated by block 2204. For example, suppose in an imagerecognition system that none of the base modules measure texture. Thenblock 2204 may determine that when a particular module that estimatestexture is included in the set of active modules then a significantnumber of errors is avoided. Block 2204 doesn't need to know either thatthe particular module estimates texture or that texture analysis ismissing in the set of base modules. Block 2204 merely needs to observethe resulting reduction in error rate achieved by added the particularmodule.

Block 2205 then sends copies of these selected modules to one or moreother systems. The amount of communication required is limited becauseonly a few selected modules are shared at any one time and the sharingmay be limited to only a few other systems at a time. Thus thecommunication may be done over a loosely coupled peer-to-peer network,such as the Internet, and does not require an ultra-high-bandwidth localarea network or other high-bandwidth, low-latency communication channel.

Block 2206 receives the modules that have been sent by the 2205 blocksin other systems.

Block 2207 performs a delayed-decision evaluation of each receivedmodule by the process illustrated in FIG. 4, where the performancecriterion is the incremental improvement in performance when thereceived module is added to the collection of modules on the givensystem. Because each system has a different collection of modules, it isexpected that a module that contributes significant improved performanceon one system may fail to contribute on another system that mightalready have other modules that can recognize the same things.Therefore, when block 2207 accepts or rejects the one-sided hypothesis,it reports back the result to the system from which it received a givenmodule. The system originating the module will be able to tell fromthese reports how much a given module has contributed to diversity inother systems.

The system continues its normal operation, continuing to receive dataand patterns to be recognized. Therefore, control returns to block 2202and the process continues and may continue indefinitely. Collectivelythe set of systems continue to improve each of the modules, to createnew modules, and to continue to increase the diversity of the collectionof modules.

FIG. 23 is a flowchart of a process of recognition by feedback ofdelayed-decision training on automatically labeled data. The discussionof FIGS. 3 and 6 has already described how delayed-decision training canbe used to correct the labels in the training data. FIG. 23 shows how,in the one embodiment, this principle may be extended to make a moreaccurate recognition system.

Block 2301 automatically labels some amount of data. That is, it runsthe recognition process on the data using the recognition output tolabel the data. In one embodiment, the recognition will be the bestavailable recognition system, using all available classifier modules.

Block 2302 treats the labeled data as training data for a particularclassifier module. For example, in speech recognition it could be usedas training data for acoustic modeling. It will be used as training datafor delayed-decision training.

Block 2303 creates alternative model sets from alternative labelings ofthe data labeled in block 2301. In one embodiment, alternative labelsmay come from the results of the recognition system used in block 2301.In one embodiment, the recognition system returns not only its topchoice classification but also a list of classes that score nearly aswell as the best scoring class. In another embodiment, in addition tousing one or more alternative labelings from a first recognition system,alternative labelings are obtained from one or more additionalrecognition systems.

Block 2304 obtains a set of practice data. This practice data may beobtained by any means that is normally used to obtain practice data. Inparticular, it may be obtained by automatically labeling a set of dataother than the data labeled as training data in block 2302.

In one embodiment, if the practice data is automatically labeled, itwill be labeled by a system that includes at least one classifier moduleother than the classifier module being trained in block 2302.

Block 2305 corrects the labels in the training data by feedback from theprocess of delayed-decision testing as shown in FIG. 6. In this case theallele of linked model sets are the alternative model sets created inblock 2303. The Socratic agent feedback information about whether thenull hypothesis can be rejected in favor of any of the model setsrelated to an alternative labeling. If so, the labeling is corrected tothe labeling that gives the highest performance in the delayed-decisiontesting.

Since all of the processes of blocks 2301 through 2305 are automaticwith no human labor, the entire process can be treated as a recognitionprocess. Block 2306 returns the corrected labels as the output of thismulti-stage recognition process. Every label corrected in theautomatically labeled training data represents a reduction in the errorsmade by the original recognition system used in block 2301, which in oneembodiment is the previously best available recognition system.

The process shown in FIG. 23 is very similar to the delayed-decisiontraining process shown in FIG. 3. Indeed, the process shown in FIG. 23is one embodiment of delayed-decision training. The main differencebetween the process shown in FIG. 23 and the process shown in FIG. 3 isthat FIG. 23 obtains more than one label value for any automaticallylabeled training sample. For training purposes, in the embodiment shownin FIG. 3, if the null hypothesis is rejected in favor of not trainingon a particular training sample, then it is sufficient to mark theparticular training sample so as to be skipped in any subsequenttraining. For producing a better recognition result, that is a correctedautomatic labeling, the embodiment in FIG. 23 obtains alternate labelvalues for any training sample for which it is considered that the labelmight be incorrect.

Viewed superficially, the process of FIG. 23 may seem somewhatparadoxical. This seeming paradox results from the ability of anautomatic recognition system to correct its own errors. If a system cancorrect its own errors why would it make the errors in the first place?Thus, the resolution of the paradox is the distinction between theoriginal recognition, made with minimal delay, and the corrections thatcan be made by means of the delayed decision testing of block 2305.Therefore, it is useful to lists the steps of the process of FIG. 23expanding out the steps in the delayed-decision testing of block 2305.FIG. 23 may also be described as comprising the following steps:

-   -   1) Obtain a set of data to be recognized. This data will be        recognized and be automatically labeled so that it can be used        as labeled training data. The purpose will not be training for        the sake of training but rather delayed-decision training for        the sake of obtaining feedback to correct the automatic        labeling.    -   2) Automatically label the obtained data with multiple labels.    -   3) For each training sample, create an allele of linked models        in which each model is created by training on the given training        sample with a particular one of the multiple labels.    -   4) Obtain a set of practice data. In one embodiment the practice        data may also be automatically labeled. In one embodiment, the        practice data and its automatically generated labels are        obtained from the on-going operational use of one or more        recognition systems.    -   5) Test the comparative performance of the linked models on the        practice data.    -   6) Correct the labels on the original set of data to be        recognized whenever the best performing model on the practice        data is associated with a label different from the chosen,        top-scoring label in the original recognition.    -   7) Return the labels as corrected as the final results of a        multi-stage recognition process.

As an illustrative example, consider a continuous speech recognitionsystem. In recognition of continuous speech, many different wordsequences must be hypothesized and evaluated. In one embodiment, theresults of evaluating these word sequences are organized into a resultslattice. For a typical position in the sentence, this results latticecontains results for more than one word that might be the word occurringat that point in the spoken sentence. In this example embodiment,alternative word labels may easily be obtained by associating eachposition in the spoken utterance with all the word labels that occur atthe corresponding position in the result lattice.

As a second illustrative example, consider an image recognition task inwhich several different image analysis methods are available. Assumethat a separate recognition system is built based on each of the imageanalysis methods. In this example embodiment, alternative labels may beobtained for each part of the image by listing all of the differentlabels that occur among the collection of recognition systems.

One description of an example embodiment of the improved recognitionprocess is as a multi-stage process including the following steps:

-   -   1) Obtain recognition results of a first recognition system. For        each sample of data, obtain a set of alternative labels. These        labels may be all the best matching class labels from a single        recognition system. They may be the total set of class label        results from a plurality of recognition systems. These labels        may be used for delayed-decision training of one or more        recognition systems, possibly including the first recognition        system.    -   2) Create a model for each alternative label for each training        sample. Create a linked set of alternative models from the        models created from each particular training sample.    -   3) Obtain a set of practice data. This practice data may be from        a single recognition system or from a plurality of recognition        systems that share the set of linked models. This practice data        may be fully or partially labeled manually or may be labeled        fully automatically. In particular, this practice data may be        recognition data obtained during the operational use of one or        more recognition systems.    -   4) Measure comparative performance of the linked models from        alternative labels for a particular training sample. One        embodiment of this comparative performance testing is        delayed-decision testing of a null hypothesis that all the        alternative models have the same performance. In this        embodiment, do not proceed to step 4 until the null hypothesis        is rejected at a statistically significant level.    -   5) For each training sample set the label to agree with the best        performing model. That is, correct the label if the model for        one of the alternative labels performs better than the model for        the original label.    -   6) Report the corrected labels as the final recognition results        for the multi-stage recognition process.

FIG. 24 is a flowchart of a process of sharing resources in thesimultaneous recognition of many channels. In one embodiment, itprovides a more cost-effective implementation of very large recognitionsystems, such as a system with multiple Socratic controllers each withmany lower-level classifier modules. It also helps make the complexprocess of improved recognition by feedback from delayed-decisiontraining as shown in FIG. 23 more practical.

Block 2401 obtains multiple channels of data to be recognized. In oneembodiment there may be hundreds or thousands of channels of data to berecognized.

Block 2402 runs the recognition process on a multi-processor network.The processors only need to be loosely coupled, say through apeer-to-peer network such as the Internet. In one embodiment, themultiple processors will be running multiple recognition systems withknowledge sharing and joint training as illustrated in FIGS. 21 and 22.

Block 2403 distributes specialized models or data. In one embodiment ofa Socratic controller a particular lower-level classifier modules may beactive for only a small fraction of the data space. By distributing suchspecialized classifier modules to particular processors in themulti-processor network, the knowledge representation in a particularspecialized classifier module does not need to be copied to everyprocessor in the network. In one embodiment, the classifier modules andone or more decision trees are distributed among a peer-to-peer networkof computers. A decision tree assigns particular computers in thenetwork to do particular tasks.

One embodiment of such a decision tree works as follows: A taskassignment is characterized by a 3-tuple, (DataSample, ModelID,ProcessorAndModuleID). The component DataSample in the 3-tuple is asample of data to be recognized. The ModelID is an abstract identifierthat indicates that a particular model or set of models is to be matchedagainst the particular data sample. Initially, only the DataSample andpossibly the ModelID values are filled in. In some cases, the ModelID isunspecified, which means that the set of models is determined by theclassifier module that gets assigned to this particular task. TheProcessorAndModuleID get filled in when the decision tree analysis getsto a leaf node of the tree. In this one embodiment, each node in thedecision tree applies a test either to the DataSample or to the ModelID.Based on the result of this test, processing continues to a particularnode in the next lower level in the decision tree. The processing forthis next node may be done on a different computer, as determined byinformation that is stored associated with the parent node. When thedecision tree process gets to a leaf node, that is a node without anysuccessor nodes, the assignment of the task to a particular processor ismade according to information associated with the given leaf node. Inone embodiment, this assignment information may include the assignmentof the classification task to a particular module residing on anassigned computer. In one embodiment, there may be many identical copiesof a given module, including copies of the associated models, so aprocessor may be assigned from a list of several processors. In thisembodiment, the assignment is made in part to balance the processionload among the computers in the network.

Other embodiments may be used, depending on the application andproperties of the computer network and the software. The corecharacteristic is that there are a large number of computers workingcooperatively on the simultaneous recognition of many data streams. Fordelayed-decision training and delayed-decision testing, thischaracteristic means that the amount of automatically labeled practicedata is proportional to the number of data streams. Therefore, theamount of elapsed time required to accumulate a statisticallysignificant amount of evidence is reduced proportionately to the inverseof the number of data streams. As a consequence, the amount of time thatit takes to accumulate evidence and feedback information to correctlabels in a recognition is also reduced in proportion to the inverse ofthe number of data streams. For example, if there are one thousandactive data streams, then the delay to get corrected labels is reduce bya factor of one thousand.

Block 2405 partitions the data according to the decision tree in oneembodiment of the Socratic controller. This decision tree classifier mayitself be distributed through the network so that not every processorneeds to have a copy of the lower branches of the decision tree.

Block 2404 recognizes multiple channels simultaneously. Each stream ofdata is sent to one or more processor that contain specializedclassifier modules as determined by the partition of the Socraticcontroller and the active set of lower-level classifier modules for eachdata item.

Block 2405 performs label correction using delayed decision trainingfeedback as shown in FIG. 23. Because there are many channels beingrecognized, the time that is required to accumulate statisticallysignificant rejection of the null hypothesis and the correspondingfeedback is proportionately reduced.

In one embodiment, the process shown in FIG. 24 may be used to reducethe delays and expense of the multi-stage recognition process shown inFIG. 23. In this embodiment, for each stream of data, top choice andalternate labels are produced. For each automatically labeled trainingsample, an allele of linked model sets is created by block 2303 of FIG.23. The performance testing of an allele of these linked models,however, is not limited to the particular recognition system thatcreates the allele. Each allele is transmitted to other recognitionsystems, each of which collects comparative performance information andtransmits this information back to the originating recognition system,which accumulates this information to eventually reject the nullhypothesis in favor of the model corresponding to one of the labelchoices for the particular training sample associated with a givenallele.

As an illustrative example, consider a continuous speech recognitionsystem that is provided to the public as a combined product and service.Assume that the product includes a recognition system that performs afirst recognition relatively quickly with local resources, but that alsoprovides communication to central resources for extra services andimproved, off-line recognition. Assume that the extra services includedelayed-decision training and sharing of knowledge among the systems ofthe users of the service.

One embodiment of the process for producing improved recognition resultswould include the following steps:

-   -   1) Obtain the data being recognized and the first recognition        results from each of the systems using the service, including        alternate labels from the results lattice of each local        recognition system.    -   2) Use the results of the first recognition as automatic labels        for delayed-decision training, creating a linked set of models        from the alternative labels for each automatically labeled        training sample.    -   3) Transmit each linked set of models to a (possible large)        number of other user systems. Collect comparative performance        data on each such system.    -   4) Transmit the comparative performance data to a site that has        been designated to accumulate evidence to accept or reject a        null hypothesis associated with the linked models created from        the alternative labels for a particular training sample.    -   5) When the null hypothesis is rejected in favor of one of the        alternative labels, change the label in the first recognition        results to agree with the label of the best scoring alternative        model.    -   6) In the system from which the original data to be recognized        was obtained, accumulate the label changes and report the        corrected labels as the final recognition results of the        multi-stage, improved recognition process. In the illustrative        embodiment, the label corrections may be accumulated for a        larger block, such as a complete document.

Referring now to FIG. 25, a block diagram shows a computer network forimplementing some aspects of some embodiments of the invention. Someembodiments of the invention involve a substantial plurality of modulesor systems, especially FIG. 8 and FIGS. 20-24. In addition someembodiments of the invention involve a substantial plurality of Socraticagents operating semi-autonomously at the same time. One embodiment ofthese aspects of the invention is distributed computing on a computernetwork, as illustrated in FIG. 25.

In this embodiment, each processor 2501 has a substantial amount oflocal memory 2505. As described in reference to some of the otherfigures, there is typically a substantial amount of data that is storedlocally that does not need to be shared throughout the network.Similarly because each Socratic agent has a specific, somewhat localizedhypothesis testing or pattern classification problem much of thecomputation is also done locally. Thus the interconnection network 2510does not need to have extremely high bandwidth compared to the combinedbandwidth of the communication between the processors 2501 and theirlocal memories 2503. Thus, in one embodiment the computer network may bea wide area or even global network, such as the Internet without thenetwork being overloaded with communication demands even if the totalnumber of processors is very large.

In the embodiment shown in FIG. 25, each processor has its own localdata input. As an illustrative example, consider a pattern recognitionsystem such as a handwriting recognition system, and optical characterrecognition system or a speech recognition system. For the illustrativeexample assume that software implementing an embodiment of the inventionhas been distributed to a large number of end users and that these enduser systems are running on the processors 2501 shown in FIG. 25.

In the illustrative example, each end user is routinely using theembodiment of the invention in the course of their normal work. As theembodiment of the invention is used, it continually performs patternrecognition for the given task. Because Socratic agents, such as shownin FIGS. 3 and 4, may use practice data that is automatically labeled,each system in FIG. 25 may locally create and run Socratic agents. Eachof these Socratic agents may modify an existing model or create a newmodel. These models will be communicable to other systems for whichthere are corresponding models or model sets in those other systems.Thus, the network of FIG. 25 may be the platform for one embodiment ofthe knowledge sharing illustrated in FIGS. 20-22.

FIG. 25 may also be used as the platform for one embodiment of thedistributed computing of multiple recognition channels illustrated inFIG. 24, which is in turn an implementation of one embodiment of themulti-stage recognition process illustrated in FIG. 23.

Using Socratic agents and Socratic controllers, an invention has beendescribed that can perform more robust training. In some embodiments, itis very tolerant of errors in the training set and errors in thepractice set. In some embodiments, the invention is even capable ofautomatically correcting the labels in the training data. In someembodiments, the invention scales to very large systems and provides ameans of managing joint training and cooperative recognition with manyrelated classifier modules as lower-level classifiers under a Socraticcontroller. In other embodiments, the invention also allows manyindependent classifier modules and scales to large distributed systems.

Thus, in some embodiments, the invention enables the sharing ofknowledge across classifier modules and systems. In some embodiments, itcan optimize the diversity among the classifier modules and manage theevolution and continuous improvement of a population of recognitionsystems. Finally, in some embodiments, it can take the best availablerecognition system and improve its performance by automatic correctionof the labels generated by that system.

Based on the core concept of Socratic agents and modeling knowledgeabout knowledge, some embodiments have aspects that embody one or moreof the following novel concepts. A brief summary of some of theseaspects is given in the following list of novel concepts and informaloutline of some potential claimed embodiments.

List of Some of the Novel Concepts or Properties in the Invention:

-   -   1. Pattern recognition using Socratic agents    -   2. Pattern recognition with self-aware, environment-aware        modules    -   3. Delayed-decision training; making decisions based on future        observed performance    -   4. Socratic agents that acquire knowledge from future        performance measurements (functionally equivalent to        precognition)    -   5. Tolerance of high error rate in evaluation data    -   6. Self-correction of errors in training data    -   7. Delayed decision for creation and deletion of modules or        models    -   8. Basing the decision for the creation or deletion of a model        or module on the contribution to improved performance relative        to the resources required    -   9. Socratic controller of collection of cooperating modules    -   10. Acquisition of knowledge of reliability of component modules        as a function of the data and of the results of the other        component modules    -   11. Adjusting the combining weights for a multiple module        classifier based as a function of the data and of the results of        the modules    -   12. Selecting which component module to train based on measuring        the degree of performance improvement from training the        respective component modules    -   13. Delaying the decision of which component module to train    -   14. Swapping copies of modules in a distributed multiple system        network    -   15. Locally making an estimate of a modules contribution to        diversity of the total collection of modules on a network    -   16. Locally evaluating the incremental contribution of shared        modules and reporting the evaluation to the originator of the        module    -   17. Creation of modules by non-determinism at system design        decisions    -   18. Joint knowledge acquisition by an arbitrarily large        collection of loosely coupled cooperating systems    -   19. Semi-supervised training using labels generated by a higher        stage module, correct by fiat.        Non-Legal Informal Outline of Some Potential Claimed        Embodiments:

-   1. A pattern recognition method/system including    -   a. At least one non-Socratic classifier module    -   b. At least one Socratic agent    -   c. in which Socratic agent acquires knowledge about the        knowledge of non-Socratic KS

-   2. As in 1,    -   a. in which Socratic agent does at least one of        -   i. creates and tests null hypothesis about non-Socratic            classifier module        -   ii. performs delayed decision test of a decision        -   iii. performs delayed decision training        -   iv. formulates and trains pattern recognition modeling            behavior of at least one classifier module        -   v. feeds back information about correctness of labeled data            item        -   vi. selects active subset from a plurality of classifier            modules        -   vii. combines results from a plurality of classifier modules        -   viii. manages joint training of a plurality of classifier            modules        -   ix. shares knowledge with at least one other Socratic agent            Delayed Decisions:

-   3. As in 2    -   a. in which Socratic agent does at least one of        -   i. creation of an allele of linked model sets        -   i. delayed decision training        -   ii. delayed decision testing        -   iii. feed back of knowledge        -   iv. correction of labels        -   v. structural learning        -   iv. sharing of knowledge

-   4. As in 3, further comprising:    -   a. creation of allele of linked model sets from a decision point        in standard process    -   b. delayed decision testing

-   5. As in 3, further comprising:    -   a. Obtaining a training sample with associated label    -   b. creation of paired-model allele from training or not training        on given sample    -   c. Delayed-Decision Training

-   6. As in 3, further comprising    -   a. correction of labels        Delayed-Decision Recognition

-   7. As in 6, further comprising:    -   a. doing recognition to automatically label data    -   b. delayed-decision training on labeled data    -   a. Delay transmission of recognition results    -   b. Using corrected labels as final recognition results

-   8. As in 2, further comprising:    -   a. Multiple channels of recognition; data received real-time on        multiple channels    -   b. Specialized modules    -   c. Distribution of data and tasks according to data space        partition    -   d. Composite distributed processing of each channel    -   e. Feedback of performance results from multiple channels in        delayed-decision evaluation

-   9. As in 8, further comprising:    -   a. Doing recognition to automatically label data on multiple        channels    -   b. Delayed-decision training applied to models used in multiple        recognition channels    -   c. Feedback of label correction    -   d. Use of corrected labels as revised recognition results for        each channel        Structural Learning:

-   10. As in 3, further comprising    -   a. Socratic agent does delayed decision creation or deletion of        models

-   11. As in 3, further comprising    -   a. Socratic agent does delayed decision insertion or deletion of        an element in a data structure

-   12. As in 11, in which    -   a. data structure is a graphical structure with nodes and arcs,        and    -   b. at least one arc is inserted or deleted

-   13. As in 3    -   a. In which Socratic agent uses one-shot learning to create at        least one of a new model and a new element within a structure.        Socratic Controllers:

-   14. As in 2,    -   a. in which at least one Socratic agent is a Socratic        controller,    -   b. further comprising a plurality of classifier modules        associated with said Socratic controller    -   c. in which said Socratic controller does at least one of        -   i. selects active subset of associated plurality of            classifier modules from data received other than output            results from said plurality of associated classifier modules        -   ii. selects active subset of associated plurality of            classifier modules based in part on output results from said            plurality of associated classifier modules        -   iii. combines results from said plurality of associated            classifier modules into composite result

-   15. As in 14    -   a. In which Socratic controller partitions the data space

-   16. As in 15, further comprising:    -   a. Plurality of associated classifier modules    -   b. Socratic controller models the performance of associated        classifier modules in part based on the region of data space

-   17. As in 2, further comprising:    -   b. Plurality of associated lower-level classifier modules    -   c. Subset of associated classifier modules are trained on a        given training sample    -   d. Delayed-decision selection of subset to be trained based on        measurements of performance of training each candidate        lower-level classifier module

-   18. As is 2, further comprising    -   b. Plurality of associated classifier modules    -   c. Socratic controller combines the results of the associated        classifier modules in a composite result    -   d. Combining rule depends on parameters estimated by the        Socratic controller    -   e. Estimates of combining parameters depend at least in part on        data values

-   19. As in 18, in which    -   a. Estimates of combining parameters depends at least in part on        output results of associated classifier modules        Sharing Knowledge

-   20. As in 2, further comprising    -   a. Measuring conditional correlations of errors

-   21. As in 20, further comprising    -   a. Creating independent modules based on measured independence        of errors

-   22. As in 2, further comprising    -   a. Shares communicable knowledge items among modules    -   b. Delayed-decision testing of performance of models in new        module    -   c. Feed back of performance measurements

-   23. As in 2, further comprising    -   a. Multiple systems    -   b. Share modules    -   c. Delayed decision testing of diversity (incremental        performance in context)

-   24. As in 2, further comprising    -   a. Multiple systems    -   b. Sharing modules    -   c. Continued independent training    -   d. Different data for different systems    -   e. Comparison of performance (on shared data)**    -   f. Management of evolution of population of system designs        Other claims:    -   1) Automatic labeling of practice data    -   2) Using a first classifier to automatically label training and        practice data for a second, simplified classifier    -   3) Evolution of a population of recognition systems    -   4) Using a decision tree for the higher-level pattern classifier        in a Socratic controller    -   5) Choosing different objectives for different nodes in a        decision tree

It should be noted that although the flow charts provided herein show aspecific order of method steps, it is understood that the order of thesesteps may differ from what is depicted. Also two or more steps may beperformed concurrently or with partial concurrence. Such variation willdepend on the software and hardware systems chosen and on designerchoice. It is understood that all such variations are within the scopeof the invention. Likewise, software and web implementations of thepresent invention could be accomplished with standard programmingtechniques with rule based logic and other logic to accomplish thevarious database searching steps, correlation steps, comparison stepsand decision steps. It should also be noted that the word “component” asused herein and in the claims is intended to encompass implementationsusing one or more lines of software code, and/or hardwareimplementations, and/or equipment for receiving manual inputs.

The foregoing description of embodiments of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the invention. Theembodiments were chosen and described in order to explain the principalsof the invention and its practical application to enable one skilled inthe art to utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated.

1. A computer-implemented pattern recognition method, comprising: creating electronically a linkage between a plurality of models within a classifier module within a pattern recognition system such that any one of said plurality of models may be selected as an active model in a recognition process; creating electronically a null hypothesis between at least one model of said plurality of linked models and at least a second model among said plurality of linked models; accumulating electronically evidence to accept or reject said null hypothesis until sufficient evidence is accumulated to reject said null hypothesis in favor of one of said plurality of linked models or until a stopping criterion is met; transmitting at least a portion of the electronically accumulated evidence or a summary thereof to accept or reject said null hypothesis to a pattern classifier module.
 2. A pattern recognition method as in claim 1, further comprising: subsequently performing recognition in which, when one null hypothesis is rejected in favor of a particular one of said plurality of linked models, said particular model is selected as the active model in said classifier module.
 3. A pattern recognition method as in claim 1, further comprising: obtaining a set of training data for training said classifier module; obtaining a particular training sample for said classifier module and an associated label for said training sample; creating a first model for said classifier module by training said classifier module on said set of training data not including said particular training sample; creating a second model for said classifier module by training said classifier module on said set of training data including said particular training sample; creating said linkage of said plurality of models in which said plurality of models includes at least said first model and said second model.
 4. A pattern recognition method as in claim 3, further comprising: annotating said particular training sample with the information obtained from said accumulating of evidence to accept or reject said null hypothesis.
 5. A pattern recognition method as in claim 4, further comprising: performing subsequent training skipping training samples and training with changed labels on the training samples in accord with the annotation obtained from said accumulation of evidence to accept or reject said null hypothesis.
 6. A pattern recognition method as in claim 1, further comprising obtaining a plurality of models resulting from different decisions at a decision point; and creating said linkage among the plurality of models resulting from the decision point.
 7. A pattern recognition method as in claim 1, further comprising obtaining a plurality of models differing from each other by having a differing number of elements in a given model data structure; creating said linkage among the plurality of models having the differing number of elements in the given data structure; creating electronically a null hypothesis between at least one model of said plurality of linked models and at least a second model among said plurality of linked models; accumulating electronically evidence to accept or reject said null hypothesis until sufficient evidence is accumulated to reject said null hypothesis in favor of one of said plurality of linked models where the rejection criterion is based at least in part on a measure of the marginal cost for the differing number elements or until a stopping criterion is met; transmitting at least a portion of the electronically accumulated evidence or a summary thereof to accept or reject said null hypothesis to a pattern classifier module.
 8. A pattern recognition method as in claim 7, wherein the given data structure is a collection of lower-level models and the elements that differ in number are the lower-level models.
 9. A pattern recognition method as in claim 8, further comprising creating at least one lower-level model by one-shot learning, and wherein the lower-level models differ in number at least in part due to the models created by one-shot learning.
 10. A pattern recognition method as in claim 7, wherein the given data structure is a graphical structure and the elements that differ in number are arcs and nodes. 